bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel pyridinium salts as cationic thermal and photoinitiators and their photosensitization properties
Authors: Takahashi Eiji , Sanda Fumio , Endo Takeshi
Published: August 2002

Novel pyridinium salts [N‐(α‐phenylbenzyl)‐, N‐(1‐naphthylmethyl)‐, or N‐cinnamyl p‐ or o‐cyanopyridinium hexafluoroantimonates] were synthesized by the reaction of p‐ or o‐cyanopyridine and the corresponding bromides followed by anion exchange with KSbF6. These pyridinium salts polymerized epoxy monomers at lower temperatures than previously reported for N‐benzyl‐2‐cyanopyridinium hexafluoroantimonate. The o‐substituted pyridinium salts showed higher activity than the p‐substituted ones, and the crosslinked epoxy polymers cured with these initiators showed higher glass‐transition temperatures. These pyridinium salts photoinitiated radical polymerization as well as cationic polymerization. The photopolymerization was accelerated by the addition of aromatic ketones as photosensitizers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1037–1046, 2002
New liquid‐crystal alignment agents based on fluorinated polyimides with trifluoromethyl‐substituted benzene or diphenylether in the side chain
Authors: Liu J. G. , Li Z. X. , Wu J. T. , Zhou H. W. , Wang F. S. , Yang S. Y.
Published: August 2002

Fluorinated copolyimides derived from 4,4′‐oxydiphthalic anhydride (ODPA) with 4,4′‐oxydianline (ODA) and trifluoromethyl‐containing aromatic diamines have been synthesized and characterized. The trifluoromethyl‐containing diamines include 2,4‐diamino‐3′‐trifluoromethylazobenzene, 2,4‐diamino‐1‐[(4′‐trifluoromethylphenoxy) phenyl] aniline, 3,5‐diamino‐1‐[(4′‐trifluoromethylphenoxy) phenyl] benzamide, 3,5‐diamino‐1‐[(3′‐trifluoromethyl) phenyl] benzamide, 1,4‐bis(4′‐aminophenoxy)‐2‐(3′‐trifluoromethylphenyl) benzene, 3,5‐diaminobenzenetrifluoride, 4,4′‐diamino‐4″‐(p‐trifluoromethyl phenoxy) triphenylamine, and 4‐[(4′‐trifluoromethylphenoxy) phenyl]‐2,6‐bis(4″‐aminophenyl)pyridine. Strong and flexible copolyimide films, produced by casting the polyamic acid solution followed by thermal imidization, exhibited great thermal stability and high mechanical properties. The polyimides had an ultraviolet–visible absorption cutoff at 330–340 nm and pretilt angles as high as 20° for nematic liquid crystals, making them great potential candidates for advanced liquid‐crystal display applications. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1583–1593, 2002
Thermoelectric behavior (PTC) of carbon black‐containing TPX/UHMWPE and TPX/XL‐UHMWPE blends
Authors: Mironi‐Harpaz I. , Narkis M.
Published: August 2002

This article describes the structure and electrical performance of positive‐temperature‐coefficient/negative‐temperature‐coefficient (PTC/NTC) effects of the following three‐component blends: poly(4‐methyl pentene‐1)/ultra‐high molecular weight polyethylene/carbon black (TPX/UHMWPE/CB), poly(4‐methyl pentene‐1)/crosslinked‐ultra‐high molecular weight polyethylene/carbon black (TPX/XL‐UHMWPE/CB), and γ‐irradiated, compression‐molded plaques of these blends. CB particles are preferentially attracted to the UHMWPE and XL‐UHMWPE particles, which constitute the dispersed phase within the TPX matrix, but practically cannot or can only very slightly penetrate them because of their extremely high viscosity. Thus, CB particles initially form conductive networks on the UHMWPE phase; this is followed by distribution in the TPX matrix, electrically connecting the CB‐covered UHMWPE particles. This unusual CB distribution results in a reduced percolation threshold of all blends. A double‐PTC effect is exhibited by the XL‐UHMWPE‐containing samples. Irradiation of compression‐molded plaques improves their thermoelectric behavior by amplifying the PTC effect and reducing the NTC effect. A schematic model of the double‐PTC effect is suggested, describing the morphological changes of 70TPX/30XL‐UHMWPE/CB blends at different stages of heating with respect to their thermoelectric behavior. Irradiation of TPX/UHMWPE/CB plaques converts these systems into high‐intensity PTC materials free of the NTC effect. © 2001 John Wiley & Sons, Inc. J Polym Sci B Part B: Polym Phys 39: 1415–1428, 2001
Effect of crystallization on oxygen‐barrier properties of copolyesters based on ethylene terephthalate
Authors: Polyakova A. , Stepanov E. V. , Sekelik D. , Schiraldi D. A. , Hiltner A. , Baer E.
Published: August 2002

The effect of crystallization from the glassy state (cold crystallization) on the oxygen‐barrier properties of copolyesters based on ethylene terephthalate with up to 10 mol % isophthalate, phthalate, or naphthalate was examined. Generally, crystallization affected diffusivity D more than solubility S; thus, the reduction in permeability P reflected primarily a reduction in D. Systematic changes in crystallinity made it possible to test free‐volume concepts in which permeation of a small gas molecule through a semicrystalline polymer is viewed as proceeding through the amorphous regions with an increased pathway (tortuosity) imposed by plateletlike crystallites. Of the copolymers studied, those with the highest isophthalate or phthalate content (10 mol %) conformed to the simple two‐phase model with constant densities of an impermeable crystalline phase and a permeable amorphous phase. Within the two‐phase model, solubility S correlated linearly with the volume fraction of the amorphous phase, and diffusivity D depended on crystallinity in accordance with the Nielsen model for randomly dispersed platelets with an aspect ratio of 4. The reduction in permeability of the other examined copolyesters could not be described only by the filler effect of crystallites. Data on solubility demonstrated a decrease in amorphous‐phase density upon cold crystallization (de‐densification) like that previously reported for polyethylene terephthalate. Increasing the isophthalate or phthalate content reduced the de‐densification effect, and 10 mol % of these comonomers was sufficient to eliminate the effect altogether. In contrast, 10 mol % naphthalate did not prevent de‐densification. This was attributed to different effects of kinked and linear comonomers on chain packing in the amorphous phase. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1911–1919, 2001
Synthesis and ionic conductivity of hyperbranched poly(glycidol)
Authors: Xinling Wang , Jianjun Chen , Ling Hong , Xiaozhen Tang
Published: August 2002

A novel hyperbranched poly(glycidol) (HPG) was prepared and characterized. The synthesized HPG was used as a substrate of a polymer electrolyte. The ionic conductivity of a blend of HPG, polyurethane (PU), and salt was studied. The ionic conductivity of HPG/PU/LiClO4 was about 6.6 × 10−6 S · cm−1 at 20 °C and 6.3 × 10−4 S · cm−1 at 60 °C. The results indicated that HPG showed higher solubility for salt than linear polyether when both had the same [O]/[Li+] molar ratio. The main reason was that more cavities and a lower degree of chain entanglement in HPG resulted in a lower glass‐transition temperature and were beneficial for decreasing the aggregation of salt or enhancing the ionic conductivity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2225–2230, 2001
Serum KL‐6 levels in pediatric patients: Reference values for children and levels in pneumonia, asthma, and measles patients
Authors: Imai Takehide , Takase Masato , Takeda Sachiyo , Kougo Toshiaki
Published: August 2002

Serum KL‐6 reflects alveolar damage and regeneration of type II pneumocytes, indicating disease activity in various interstitial lung diseases. We conducted a descriptive and observational multiple case‐control study to determine the distribution of serum KL‐6 levels in pediatric patients with or without respiratory diseases. Subjects were recruited from the patients of a teaching hospital in the suburb of Tokyo. A consecutive series of 401 children (0–16 years old) underwent blood sampling for many clinical reasons. They comprised the following four groups: pneumonia (n = 96), bronchial asthma (n = 101), measles (n = 102), and nonrespiratory diseases (n = 102) as a control group.

Standard upper limits of serum KL‐6 in a group of children with nonrespiratory disease were 250 U/mL, or half the adult level. No gender or age differences were observed. Elevated serum KL‐6 concentrations were observed in severe pneumonia, acute exacerbations of asthma, and measles pneumonia. In the measles group, KL‐6 values reflected the presence and severity of complicating pneumonia.

We conclude that serum KL‐6 levels exceeding 250 U/mL were rarely observed in children without respiratory diseases. In contrast, a substantial proportion of children with common respiratory diseases showed mild to moderate increases in serum KL‐6 levels. Elevated serum KL‐6 in these children may reflect the presence of alveolar damage, followed by regeneration of type II pneumocytes. However, in order to use serum KL‐6 as a marker of interstitial lung diseases in children, a cutoff level should be determined separately. Pediatr Pulmonol. 2002; 33:135–141. © 2002 Wiley‐Liss, Inc.
Patient‐ventilator interactions in new modes of patient‐triggered ventilation*
Authors: Abubakar Kabir M. , Keszler Martin
Published: August 2002

Recently, synchronized modes of conventional mechanical ventilation became available for neonatal ventilatory support, but there has been little information regarding details of patient‐ventilator interactions during pressure support, volume support, or any other volume‐targeted modes of synchronized ventilation in newborn infants. Our objective was to obtain comparative data on patient‐ventilator interactions and stability of delivered tidal volume (VT) for the different modes of synchronized mechanical ventilation in stable ventilated newborn infants. We examined the effects of pressure support ventilation (PSV) and volume guarantee (VG) modes of a prototype Dräger Babylog® ventilator on peak and mean airway pressures (PIP and Paw), inspiratory time (tin), and VT in 23 ventilated newborn infants. Twelve infants were studied while on assist/control (AC) and 11 on synchronized intermittent mandatory ventilation (SIMV). Mean birth weight was 1,650 ± 1,180 g, gestational age 31 ± 6 weeks, and age at time of study was 19 ± 26 days. Data for 400–600 breaths from each infant were downloaded directly from the ventilator pressure and volume‐monitoring module, and analyzed using ANOVA for repeated measures. Mean values and breath‐to‐breath variability were compared for 20‐min periods of AC or SIMV followed by PSV, PSV+VG, and back to baseline AC or SIMV.

PSV and PSV+VG led to shorter tin and thus to lower Paw, compared to AC. Mean PIP was similar across all AC modes but more variable during VG, reflecting the servocontrol of PIP. VT did not differ between AC modes, but was significantly less variable with VG added. PSV and PSV+VG led to lower and less variable PIP and Paw, compared to SIMV, because tin was shorter and every breath was supported in PSV and PSV+VG. VT was similar in SIMV, PSV, and PSV+VG, but less variable with PSV+VG. Arterial blood gas tensions were similar across all ventilation modes.

We conclude that the ventilator prototype functioned as intended. Breath‐to‐breath tidal volume variability was significantly reduced in VG modes, although not completely eliminated. Pediatr Pulmonol. 2001; 32:71–75. © 2001 Wiley‐Liss, Inc.
Osteoblasts produce soluble factors that induce a gene expression pattern in non‐metastatic prostate cancer cells, similar to that found in bone metastatic prostate cancer cells
Authors: Fu Zheng , Dozmorov Igor M. , Keller Evan T.
Published: August 2002

BACKGROUND

Progressive prostate cancer typically metastasizes to bone where prostate cancer cells gain an osteoblast‐like phenotype and induce osteoblastic metastases through unknown mechanisms. To investigate the biology of prostate cancer skeletal metastases, we compared gene expression between the non‐metastatic LNCaP cell line and its derivative cell line C4‐2B that metastasizes to bone.

METHODS

Total RNA from LNCaP and C4‐2B cell lines was isolated and used to probe membrane‐based gene arrays (Comparison 1). Additionally, LNCaP cells were incubated in the absence or presence of conditioned media (CM) from a human osteoblast‐like cell line (HOBIT) and total RNA from these cells was used to probe gene arrays (Comparison 2). Differential expression of genes was confirmed by RT‐PCR.

RESULTS

Of the 1,176 genes screened, 35 were differentially expressed between LNCaP and C4‐2B cells (Comparison 1). HOBIT‐CM induced differential expression of 30 genes in LNCaP cells (Comparison 2). Interestingly, 19 genes that were differentially expressed in C4‐2B vs. LNCaP also displayed a similar expression pattern in LNCaPs grown in HOBIT‐CM. These genes are primarily involved in motility, metabolism, signal transduction, tumorigenesis, and apoptosis.

CONCLUSIONS

These results suggest that osteoblasts produce soluble factors that contribute to the progression of prostate cancer skeletal metastases, including their transition to an osteoblast‐like phenotype. Additionally, these data provide targets to explore for further investigations towards defining the biology of skeletal metastases. Prostate 51: 10–20, 2002. © 2002 Wiley‐Liss, Inc.
Complex functions of mutant p53 alleles from human prostate cancer
Authors: Shi Xu‐Bao , Nesslinger Nancy J. , Deitch Arline D. , Gumerlock Paul H. , deVere White Ralph W.
Published: August 2002

Background

Few studies have used multiple assays to examine the functionality of mutant p53 in prostate cancer (CaP). We employed seven functional assays to study 16 representative mutant p53 alleles, six from localized and ten from metastatic CaP.

Methods

Yeast assays were employed to determine loss of function (LOF), partial function (PF), and dominant‐negative status. Assays using p53‐null Saos2 cells were used to determine whether mammalian cells transfected with mutant p53 could up‐regulate the MDR‐1 or PCNA promoters, alter IL‐6 expression or confer the ability to grow in soft agar. As a further test of gain of function (GOF), p53‐null PC3 cells stably transfected with these mutant p53 alleles were examined for cell cycle distributions.

Results

All 16 mutant p53 alleles demonstrated either total or partial LOF. All but one allele also had at least one gain of function; however, the pattern of GOF was different for each mutant allele. Alleles derived from both localized and metastatic CaP had similar GOF characteristics; however, only alleles from metastatic disease had significantly increased S‐phase fractions.

Conclusions

Different mutant p53 alleles from CaP had different, complex functional profiles. The lack of predictable patterns for these alleles suggest that each mutation may uniquely affect p53 function. Prostate 51:59–72, 2002. © 2002 Wiley‐Liss, Inc.
Folding of intracellular retinol and retinoic acid binding proteins
Authors: Burns Lora L. , Ropson Ira J.
Published: August 2002

The folding mechanisms of cellular retinol binding protein II (CRBP II), cellular retinoic acid binding protein I (CRABP I), and cellular retinoic acid binding protein II (CRABP II) were examined. These β‐sheet proteins have very similar structures and higher sequence homologies than most proteins in this diverse family. They have similar stabilities and show completely reversible folding at equilibrium with urea as a denaturant. The unfolding kinetics of these proteins were monitored during folding and unfolding by circular dichroism (CD) and fluorescence. During unfolding, CRABP II showed no intermediates, CRABP I had an intermediate with nativelike secondary structure, and CRBP II had an intermediate that lacked secondary structure. The refolding kinetics of these proteins were more similar. Each protein showed a burst‐phase change in intensity by both CD and fluorescence, followed by a single observed phase by both CD and fluorescence and one or two additional refolding phases by fluorescence. The fluorescence spectral properties of the intermediate states were similar and suggested a gradual increase in the amount of native tertiary structure present for each step in a sequential path. However, the rates of folding differed by as much as 3 orders of magnitude and were slower than those expected from the contact order and topology of these proteins. As such, proteins with the same final structure may not follow the same route to the native state. Proteins 2001;43:292–302. © 2001 Wiley‐Liss, Inc.
Proline‐induced hinges in transmembrane helices: Possible roles in ion channel gating
Authors: Tieleman D. Peter , Shrivastava Indira H. , Ulmschneider Martin R. , Sansom Mark S.P.
Published: August 2002

A number of ion channels contain transmembrane (TM) α‐helices that contain proline‐induced molecular hinges. These TM helices include the channel‐forming peptide alamethicin (Alm), the S6 helix from voltage‐gated potassium (Kv) channels, and the D5 helix from voltage‐gated chloride (CLC) channels. For both Alm and KvS6, experimental data implicate hinge‐bending motions of the helix in an aspect of channel gating. We have compared the hinge‐bending motions of these TM helices in bilayer‐like environments by multi‐nanosecond MD simulations in an attempt to describe motions of these helices that may underlie possible modes of channel gating. Alm is an α‐helical channel‐forming peptide, which contains a central kink associated with a Gly‐x‐x‐Pro motif in its sequence. Simulations of Alm in a TM orientation for 10 ns in an octane slab indicate that the Gly‐x‐x‐Pro motif acts as a molecular hinge. The S6 helix from Shaker Kv channels contains a Pro‐Val‐Pro motif. Modeling studies and recent experimental data suggest that the KvS6 helix may be kinked in the vicinity of this motif. Simulations (10 ns) of an isolated KvS6 helix in an octane slab and in a POPC bilayer reveal hinge‐bending motions. A pattern‐matching approach was used to search for possible hinge‐bending motifs in the TM helices of other ion channel proteins. This uncovered a conserved Gly‐x‐Pro motif in TM helix D5 of CLC channels. MD simulations of a model of hCLC1‐D5 spanning an octane slab suggest that this channel also contains a TM helix that undergoes hinge‐bending motion. In conclusion, our simulations suggest a model in which hinge‐bending motions of TM helices may play a functional role in the gating mechanisms of several different families of ion channels. Proteins 2001;44:63–72. © 2001 Wiley‐Liss, Inc.
Kinetics of chemical degradation of isoxaflutole: influence of the nature of aqueous buffers (alkanoic acid/sodium salt vs phosphate)
Authors: Beltran Estelle , Fenet Hélène , Cooper Jean‐François , Coste Camille‐Michel
Published: August 2002

A kinetic study of the chemical degradation of isoxaflutole (5‐cyclopropyl‐1,2‐oxazol‐4‐yl ααα‐trifluoro‐2‐mesyl‐p‐tolyl ketone) into its diketonitrile derivative (DKN), which is its active herbicide principle, in organic buffers at different pH values was carried out using a HPLC/UV detection method. The values of the pseudo‐first‐order rate constants Kobs for the reaction were calculated and compared with those previously obtained in inorganic buffers. In both cases, Kobs was found to be dependent on pH and temperature, but at pH 5.2 the degradation of isoxaflutole in CH3COOH/CH3COONa buffers was considerably faster than in KH2PO4/Na2HPO4 buffers, indicating that the compound was sensitive to the nature of the reagents used to prepare buffered solutions. The influence of phosphate and acetate concentrations and the influence of the R‐substituent in RCOOH/RCOONa buffers were investigated. For the HA/A− buffers studied, the values of Kobs were linearly dependent on HA and A− concentrations, which meant that the degradation of isoxaflutole was subject to general catalysis. The values of Kobs were also found to be dependent on the number and the position of the CH3 groups of the R‐substituent. The known degradation product of DKN (a benzoic acid derivative) was not detected throughout this study.

© 2001 Society of Chemical Industry
Chitin synthesis and inhibition: a revisit
Authors: Cohen Ephraim
Published: August 2002

Chitin is an abundant biologically important aminopolysaccharide composed of N‐acetyl‐D‐glucosamine units. Individual polymers, which are synthesized intracellularly by chitin synthase (CS), a membrane‐bound glycosyl transferase, are translocated across the plasma membrane and coalesce to form rigid crystallites. These crystallites, inter alia, are integral parts of septa and cell walls in yeast and filamentous fungi, respectively, and of cuticles in invertebrates, notably crustaceans and insects. Despite decades of intensive research, many events associated with the complexity of chitin formation and deposition are still obscure, or only partially understood. The list includes the hormonal control of CS at the transcriptional and translational levels as well as the post‐translational CS packaging; trafficking and guidance of CS clusters to proper sites in the cells and their intricate insertion into the plasma membranes; activation of the catalytic step and its control or modulation; and translocation of chitin chains across cell membranes, their orientation, fibrillogenesis and association with other extracellular structural components such as polysaccharides (fungi) and cuticular proteins (insects). Also the precise biochemical lesions inflicted by CS inhibitors, such as the acylurea insect growth regulators, are largely unclear. The recent isolation and sequencing of insect CS genes should help in elucidating various aspects of chitin biochemistry and inhibition. In particular, the large number of transmembrane segments, characteristic of the insect CS, are speculated to be involved in chitin translocation and are expected to shed light on the mode of action of acylurea insecticides.

© 2001 Society of Chemical Industry
A 27‐mer tandem repeat polypeptide in bovine amelogenin: Synthesis and CD spectra
Authors: Renugopalakrishnan V.
Published: August 2002

CD spectra of a tandem 27‐mer repeat polypeptide, Gln‐Pro‐His‐Gln‐Pro‐Leu‐Gln‐Pro‐His‐Gln‐Pro‐Leu‐Gln‐Pro‐Met‐(Gln‐Pro‐Leu)4, from bovine amelogenin synthesized by standard solid‐phase synthesis manifests an archtypical CD pattern of a β‐spiral structure in phosphate buffer at pH 5.2 and trifluoroethanol (TFE), CF3OH. β‐spiral structure is unique to a class of diverse proteins including amelogenins conferring unusual physicochemical properties. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd.
Antimicrobial activity of honokiol and magnolol isolated from Magnolia officinalis
Authors: Ho Kun‐Yen , Tsai Chi‐Cheng , Chen Chi‐Pien , Huang Jiing‐Sheng , Lin Chun‐Ching
Published: August 2002

The antimicrobial activity of honokiol and magnolol, the main constituents of Magnolia officinalis was investigated. The antimicrobial activity was assayed by the agar dilution method using brain heart infusion medium and the minimum inhibitory concentration (MIC) were determined for each compound using a twofold serial dilution assay. The results showed that honokiol and magnolol have a marked antimicrobial effect (MIC = 25 µg/mL) against Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Micrococcus luteus and Bacillus subtilis, but did not show antimicrobial activity (MIC ≥ 100 µg/mL) for Shigella flexneii, Staphylococcus epidermidis, Enterobacter aerogenes, Proteus vulgaris, Escherichia coli and Pseudomonas aeruginosa. Our results indicate that honokiol and magnolol, although less potent than tetracycline, show a significant antimicrobial activity for periodontal pathogens. Hence we suggest that honokiol and magnolol might have the potential to be an adjunct in the treatment of periodontitis. Copyright © 2001 John Wiley & Sons, Ltd.
Immunomodulatory principles of Pelargonium sidoides
Authors: Kayser O. , Kolodziej H. , Kiderlen A. F.
Published: August 2002

Extracts and isolated constituents (coumarins and phenols) of Pelargonium sidoides DC, a plant species used in folk medicine by the Southern African native population, were evaluated for their effects on nonspecific immune functions. Although this herbal medicine is also successfully employed in modern phytotherapy in Europe to cure infectious diseases of the respiratory tract, the scientific basis of its remedial effects is still unclear. Thus, functional bioassays including an in vitro model for intracellular infection with Leishmania parasites, an extracellular Leishmania growth assay, a fibroblast‐virus protection assay (IFN activity), a fibroblast‐lysis assay (TNF activity) and a biochemical assay for inorganic nitric oxides (iNO) were employed. None of the test samples revealed significant activity against extracellular, promastigote Leishmania donovani, the causative agent of human visceral leishmaniasis. In contrast, apart from the coumarin samples, all the Pelargonium extracts (EC50 <0.1–3.3 μg/mL), gallic acid (EC50 4.4 μg/mL) and its methyl ester (EC50 12.5μg/mL) significantly reduced the intracellular survival of L. donovani amastigotes within murine macrophages. These data indicate that the samples acted indirectly on Leishmania parasites, possibly by activating leishmanicidal macrophage functions. Macrophage activation was confirmed by detection of tumour necrosis factor (TNF‐α) and inorganic nitric oxides (iNO) in supernatants of sample‐treated macrophage cultures. Synthesis of iNO is a well‐known effector mechanism of macrophages against microorganisms such as Leishmania. Interestingly, blocking iNO‐synthase with L‐NMMA had no substantial effect on sample‐induced intracellular Leishmania kill. From bioassay‐guided fractionation, gallic acid and its methyl ester present in large amounts in P. sidoides and in its active extracts, were identified as the prominent immunomodulatory principle for this herbal medicine. The results, when taken together with recent reported antibacterial activity, provide a rational basis for both the traditional and the present utilization of P. sidoides in the claimed conditions. Copyright © 2001 John Wiley & Sons, Ltd.
On misinterpretation of the asymptotic property of system time‐between‐failures
Authors: Chambal Stephen P. , Keats J. Bert
Published: August 2002

If a system, not necessarily one in series, is composed of components having various time‐to‐failure distributions and components are replaced good‐as‐new as they fail, then the system time‐between‐failure distribution tends toward the exponential. Many practicing reliability engineers, incorrectly invoking this property, model their systems with an exponential time‐to‐failure. We show, under two conditions, using a hypothetical fleet of vehicles, the severity of this error. Modeling time‐to‐failure as exponential results in gross over‐sparing and high unavailability costs as well. Copyright © 2001 John Wiley & Sons, Ltd.
Optimal control of a deteriorating process with a quadratic loss function
Authors: Al‐Fawzan M. A. , Rahim M. A.
Published: August 2002

This paper considers the optimal determination of the length of the production run and the initial setting of a process that exhibits a linear drift that can start at a random point in time. Quadratic off‐target costs and time‐based costs of maintenance and salvage value are included in the formulation. The model includes other models proposed in the literature as particular cases. Numerical examples are provided to illustrate the application of the proposed model. Copyright © 2001 John Wiley & Sons, Ltd.
Potential harmonic approximation in atomic three‐body systems with Fues–Kratzer‐type potential
Authors: Yalçin Zeynel , Şimşek Mehmet
Published: August 2002

By using the matrix form of the Fues–Kratzer‐type (FK) potential, V(r) = Ẑ(Ω)/r + Â/r2, three‐body problems of two‐electron atomic systems are solved with the PHGLP expansion method. The atomic wave functions Ψ(Ω) are constructed in terms of generalized Laguarre polynomials (GLP) and potential harmonics (PH). The calculations of the ground‐state energies of atoms from He to Si12+ are tabulated using Deng et al.'s procedure and also the effect of the new potential onto excited states of 1S Li+ are illustrated. Then, we calculated excited state energies (n1S, n = 1–3) of the atoms from He to Si12+ with the FK potential. The present results are compared with other theoretical calculations. It is pointed out that convergences of our results are more rapid than the results of the pure Coulombic interaction, and, so, this article increases the efficiency of the calculation for atomic three‐body systems. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Quantum criticality at the large‐dimensional limit: Three‐body Coulomb systems
Authors: Shi Qicun , Kais Sabre
Published: August 2002

We present quantum phase transitions and critical phenomena at the large‐dimension (D) limit for three‐body ABA Coulomb systems with charges (Q,q,Q) and masses (M,m,M). The Hamiltonian depends linearly on two parameters λ=∣Q/q∣ and κ=[1+(m/M)]−1. The system exhibits critical points with mean field critical exponents (α=0, β=½, δ=3, γ=1). We calculate the critical curve λc(κ) through which all systems undergo a continuous‐phase transition from the symmetrical configuration, the two like particles have the same distance from the reference particle, to the unsymmetrical phase. The critical curve at D→∞ limit is a convex function of κ and very similar to the one obtained at D=3 with variational calculations. We also calculated the line of zero angular correlation in the mass polarization term, which separates the symmetrical phase to an atom‐like region and a molecule‐like region. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Determination of 4‐hydroxytamoxifen in mouse plasma in the pg/mL range by gradient capillary liquid chromatography/tandem mass spectrometry
Authors: Plumb R. S. , Warwick H. , Higton D. , Dear G. J. , Mallett D. N.
Published: August 2002

Capillary high‐performance liquid chromatography (HPLC; 300 µm i.d.) coupled to tandem mass spectrometry has been used to determine the concentration of 4‐hydroxytamoxifen in mouse plasma in the pg/mL range following the administration of Tamoxifen. A limit of quantification (LOQ) of 100 pg/mL was achieved using only 25 µL of plasma. The on‐column sensitivity was determined to be 100 fg. The column performance was determined isocratically before and after the assay and showed only a 15% reduction in performance after 70 injections of plasma extract. No significant peak band broadening was observed due to the mass spectrometer interface using a standard TurboIonspray source. Copyright © 2001 John Wiley & Sons, Ltd.
Identification and characterization of Fenton oxidation products of surfactants by electrospray mass spectrometry and solid phase microextraction gas chromatography/mass spectrometry. 3. Polyethoxylated fatty alcohols and nonylphenols
Authors: Cuzzola Angela , Raffaelli Andrea , Saba Alessandro , Salvadori Piero
Published: August 2002

The Fenton reaction for the degradation of surfactants has been investigated and partial degradation products have been identified and characterized by mass spectrometry for the case of polyethoxylated nonylphenols and fatty alcohols with an average ethoxylation number of 7. The polar water‐soluble products were investigated by liquid chromatography/mass spectrometry (LC/MS) with electrospray ionization (ESI), and the volatile products leaving the mixture during the reaction were trapped by means of solid phase microextraction (SPME) and investigated by gas chromatography/mass spectrometry (GC/MS) with EI and CI ionization. The reaction leads to the shortening of the ethoxylic chain and to the oxidation of the terminal part. The formation of volatile aldehydes is also observed, corresponding to fragmentation between the hydrophobic part and the polar head. The extent of mineralization is dependent on peroxide and iron(II) concentrations. Copyright © 2001 John Wiley & Sons, Ltd.
Screening combinatorial libraries for optimal enzyme substrates by mass spectrometry
Authors: Wang Peng , Snavley Donald F. , Freitas Michael A. , Pei Dehua
Published: August 2002

A method has been developed for the rapid identification of optimal enzyme substrates from combinatorial libraries. This methodology was validated by screening a 361‐member N‐terminally formylated tripeptide library, f‐XXR (X = 19 different amino acids), for optimal substrates of Escherichia coli peptide deformylase (PDF). The library was synthesized on a solid phase via the split‐pool synthesis method. The N‐terminal formyl group was added by treating the resin with a 1:1 (mol/mol) mixture of HCO2H and DCO2D in the presence of dicyclohexylcarbodiimide. In a mass spectrum, each member of the library produced a doublet peak (separated by 1.0063 Da). Limited treatment of this library with E. coli PDF resulted in the deformylation of those peptides that are the most efficient substrates of the enzyme. The deformylated products, due to loss of the mass‐degenerate formyl group, each generated a singlet peak in the mass spectrum. Thus, the PDF product peaks were readily identified and sequenced via tandem mass spectrometry. The results showed that PDF strongly prefers a norleucine and, to a lesser extent, a phenylalanine as the N‐terminal residue, whereas it has little selectivity at the penultimate position. This result is in excellent agreement with the literature data and therefore demonstrates the methodology as an effective approach to the identification of optimal enzyme substrates. This method should be generally applicable to other enzymes as well as synthetic catalysts. Copyright © 2001 John Wiley & Sons, Ltd.
Time‐of‐flight mass spectrometric analysis of ion formation in hypervelocity impact of organic polymer microspheres: comparison with secondary ion mass spectrometry, 252Cf mass spectrometry and laser mass spectrometry
Authors: Kissel Jochen , Krueger Franz R.
Published: August 2002

Unisized 1.6‐µm polystyrene microspheres coated with PEDOT (polyethylene‐dioxythiophene) were accelerated to speeds of 6–16 km/s and shot onto a silver target. Either positive or negative ions, both instantaneously formed by the impact process, have been analyzed by time‐of‐flight mass spectrometry (TOF). Apparently, the processes that control the formation of ions of either polarity depend on the impact velocity. Comparing the results with those of secondary ion mass spectrometry with primary ion energy in both the elastic and the inelastic (252Cf‐MS) energy loss regimes, some reaction mechanisms of the polymer ions for different energy densities could be elucidated. Some aspects of ion formation are also related to those found in pulsed laser ion generation from these microspheres. This investigation was performed in order to further improve the method of analyzing the organic fraction of interstellar, interplanetary, and cometary dust particles impinging on the targets of the ‘CIDA’ time‐of‐flight (TOF) mass spectrometers on‐board the NASA comet missions ‘STARDUST’ and ‘CONTOUR’. Copyright © 2001 John Wiley & Sons, Ltd.
Friction analysis based on integral quadratic constraints
Authors: Rantzer A.
Published: August 2002

Passivity arguments have long been used in the analysis of systems with friction. This paper proves a new set of integral quadratic constraints, which reduces the conservatism of such methods. The result is used to derive a quantitative bound on the amount of integrator leakage that is needed to remove stiction‐induced oscillations in a servo system.

Finally, an incremental version of the circle criterion is used to study the existence of subharmonics due to friction in a system subject to externally forced oscillations. Copyright © 2001 John Wiley & Sons, Ltd.
Quantification from overlapping Auger peak‐to‐peak heights
Authors: Asante J. K. O. , Roos W. D. , Maritz M. F.
Published: August 2002

Auger peak‐to‐ peak‐heights (APPHs) in the derivative Auger spectra can be used during quantification to determine the fractions contributing to the Auger yield. The calculated APPH is stored during sampling, whereas the spectra are sometimes discarded. When peaks overlap, only the APPH of the combined spectrum is stored. In such cases, where the original spectra are no longer available, it is impossible to extract the contribution of each of the species from a single APPH. However, if APPHs have been sampled in two separate energy regions, both with overlapping peaks of the same species, it is possible again to extract the individual contributions provided that standards of both species (taken under similar conditions) are available. Because the APPH of the sum of two spectra is not the sum of the APPHs of the contributing spectra, the procedure involves simultaneous solution of two non‐linear equations. Copyright © 2001 John Wiley & Sons, Ltd.
Detachment of alumina films from aluminium by 100 keV H+ ions
Authors: Liu Y. , Alexander M. , Koroleva E. , Skeldon P. , Thompson G. E. , Bailey P. , Noakes T. C. Q. , Shimizu K. , Habazaki H.
Published: August 2002

Irradiation of aluminium covered by anodic oxide films 3–14 nm thick using 100 keV H+ ions is shown to result in detachment of the oxide film. A dose of 6.6 × 1016 H+ ions cm−2 on a 6.5 nm thick film causes the removal of large pieces of oxide with dimensions at least 15 µm. Atomic force microscopy analysis shows that the location of the failure is within ∼1 nm of the metal/oxide interface. The large aspect ratio (width to thickness) of the detached pieces is thus ∼2000 : 1 and indicates that there is a disruption of the oxide bonding over large areas. The bombardment also results in the formation of blisters with diameters up to several hundred nanometres in the oxide, accompanied by shallow depressions, ∼5 nm deep in the underlying metal. The detachment is suggested to be associated with either condensation of vacancies generated in the metal by the H+ ions or accumulation of hydrogen atoms deposited in the metal by the ion beam in the region of the metal/oxide interface. Although the beam energy and dose were expected to cause some disruption in the implanted material, the complete detachment of large areas of oxide was not anticipated. In fact, this appears to be the first time such gross detachment of an anodic film by H+ ion irradiation has been reported. Copyright © 2002 John Wiley & Sons, Ltd.
Estimating cancer prevalence using mixture models for cancer survival
Authors: Phillips Norman , Coldman Andrew , McBride Mary L.
Published: August 2002

Knowledge of cancer prevalence is useful for estimating the ongoing level of resources utilized in the treatment of disease and is of some public health interest. Cancer prevalence is estimated first as the proportion of persons previously diagnosed (PD) with cancer that are still alive; and second as the proportion of individuals in the population who were previously diagnosed with cancer and who have not been cured (NC). The proportion of cases that are cured is estimated by assuming that the cured and uncured cases have distinct survival patterns. The hazard for cured cases is assumed to be a multiple of the hazard from causes other than cancer in the general population. The hazard for uncured cases is assumed to have two independent components: one corresponding to the disease‐specific hazard, and the other a multiple of the population hazard from ‘other causes’. Future prevalence estimates are obtained by projecting the survival of current prevalent cases as well as the survival of future incident cases. Copyright © 2002 John Wiley & Sons, Ltd.
Use of a density equalizing map projection in analysing childhood cancer in four California counties
Authors: Merrill Deane W.
Published: August 2002

In this study, 401 cases of childhood cancer in four California counties in 1980–1988 were analysed with the innovative methodology of density equalizing map projections. The data were originally collected and analysed by the California State Department of Health Services (DHS). In addition to the new analytic technique, the present analysis used population data more detailed and more accurate than those in the DHS analysis. The geographic boundaries of the 259 census tracts in the study area were adjusted according to population at risk so as to make population density everywhere constant; then the 401 case locations were plotted on the density equalized map. If risk is everywhere equal, the resulting distribution of cases should be uniform except for statistical variation. The metric used was a measure of the variability of the density of cases on the density equalized map. The same metric was calculated for independent samples of artificial cases, generated under the null hypothesis of equal risk. The slight geographic non‐uniformity observed among the real cases is well within the limits of variation observed in the samples of artificial cases. In agreement with results published by DHS, we conclude that there is no evidence for geographic variation of risk among the cases studied. Subsets of the data, selected by age, sex, race, time period and cancer site, yielded similar negative results. Copyright © 2001 John Wiley & Sons, Ltd.
A generalized concordance correlation coefficient for continuous and categorical data
Authors: King Tonya S. , Chinchilli Vernon M.
Published: August 2002

This paper discusses a generalized version of the concordance correlation coefficient for agreement data. The concordance correlation coefficient evaluates the accuracy and precision between two measures, and is based on the expected value of the squared function of distance. We have generalized this coefficient by applying alternative functions of distance to produce more robust versions of the concordance correlation coefficient. In this paper we extend the application of this class of estimators to categorical data as well, and demonstrate similarities to the kappa and weighted kappa statistics. We also introduce a stratified concordance correlation coefficient which adjusts for explanatory factors, and an extended concordance correlation coefficient which measures agreement among more than two responses. With these extensions, the generalized concordance correlation coefficient provides a unifying approach to assessing agreement among two or more measures that are either continuous or categorical in scale. Copyright © 2001 John Wiley & Sons, Ltd.
Automated analysis, verification and testing
Authors: Tracey Nigel , Penix John , Visser Willem
Published: August 2002

In Software Testing, Verification and Reliability, NIGEL TRACEY, JOHN PENIX and WILLEM VISSER present a special issue for researchers and developers interested in automated verification, analysis and testing of software, exploring new collaborations and aiming to increase the level of co‐operation between communities. Copyright © 2001 John Wiley & Sons, Ltd.
Expression and acquisition of the conditioned place preference response to cocaine in rats is blocked by selective inhibitors of the enzyme N‐acetylated‐α‐linked‐acidic dipeptidase (NAALADASE)
Authors: Slusher Barbara S. , Thomas Ajit , Paul Mousumi , Schad Christina A. , Ashby Charles R.
Published: August 2002

In this study we examined the effect of 2‐(phosphonomethyl)pentanedioic acid (2‐PMPA) and GPI 5693, selective inhibitors of the enzyme N‐Acetylated‐α‐Linked‐Acidic Dipeptidase (NAALADase; glutamate carboxypeptidase II; EC no. 3.4.17.21), which cleaves glutamate from the dipeptide N‐acetyl‐aspartyl‐glutamate (NAAG), on the conditioned place preference (CPP) response to cocaine in male rats. The i.p. administration of 15 mg/kg of cocaine produced a significant CPP response. The acquisition and expression of the CPP response to cocaine was blocked by the i.p. administration of 100 mg/kg of 2‐PMPA and the p.o. administration of 30 mg/kg of GPI 5693. In contrast, neither 2‐PMPA nor GPI 5693 produced a CPP or conditioned place aversion response when administered alone. Furthermore, neither 2‐PMPA or GPI 5693 altered the expression of the CPP response to food. These results indicate that NAALADase inhibitors block the incentive motivational value of cocaine, suggesting that such agents may be of use in treating cue‐induced craving in cocaine addicts. Synapse 41:22–28, 2001. © 2001 Wiley‐Liss, Inc.
Drift design of steel‐frame shear‐wall systems for tall buildings
Authors: Park Hyo Seon , Hong Kappyo , Seo Ji Hyun
Published: August 2002

Drift design methods based on resizing algorithms are presented to control lateral displacements of steel‐frame shear‐wall systems for tall buildings. Three algorithms for resizing of structural members of the steel‐frame shear‐wall systems are derived by formulating the drift design process into an optimization problem that minimizes lateral displacement of the system without changing the weight of a structure. During the drift design process, cost‐effective displacement participation factors obtained by the energy method are used to determine the amount of material to be modified instead of calculating sensitivity coefficients. The overall structural design model with the drift design method for the steel‐frame shear‐wall systems is proposed and applied to the structural design of three examples. As demonstrated in the examples, the lateral displacement and interstorey drift of a frame shear‐wall system can be effectively designed by the drift design method without the time‐consuming trial‐and‐error process. Copyright © 2002 John Wiley & Sons, Ltd.
Teaching science problem solving: An overview of experimental work
Authors: Taconis R. , Ferguson‐Hessler M.G.M. , Broekkamp H.
Published: August 2002

The traditional approach to teaching science problem solving is having the students work individually on a large number of problems. This approach has long been overtaken by research suggesting and testing other methods, which are expected to be more effective. To get an overview of the characteristics of good and innovative problem‐solving teaching strategies, we performed an analysis of a number of articles published between 1985 and 1995 in high‐standard international journals, describing experimental research into the effectiveness of a wide variety of teaching strategies for science problem solving. To characterize the teaching strategies found, we used a model of the capacities needed for effective science problem solving, composed of a knowledge base and a skills base. The relations between the cognitive capacities required by the experimental or control treatments and those of the model were specified and used as independent variables. Other independent variables were learning conditions such as feedback and group work. As a dependent variable we used standardized learning effects. We identified 22 articles describing 40 experiments that met the standards we deemed necessary for a meta‐analysis. These experiments were analyzed both with quantitative (correlational) methods and with a systematic qualitative method. A few of the independent variables were found to characterize effective strategies for teaching science problem solving. Effective treatments all gave attention to the structure and function (the schemata) of the knowledge base, whereas attention to knowledge of strategy and the practice of problem solving turned out to have little effect. As for learning conditions, both providing the learners with guidelines and criteria they can use in judging their own problem‐solving process and products, and providing immediate feedback to them were found to be important prerequisites for the acquisition of problem‐solving skills. Group work did not lead to positive effects unless combined with other variables, such as guidelines and feedback. © 2001 John Wiley & Sons, Inc. J Res Sci Teach 38: 442–468, 2001