bluuebunny/crossref_metadata_2025 huggingface dataset:
Multistep mass spectrometry of heterocyclic amines in a quadrupole ion trap mass analyser
Authors: Toribio Francisca , Moyano Encarnación , Puignou Lluís , Galceran Maria Teresa
Published: September 2002

The fragmentation of heterocyclic amines (HAs) in an ion trap was studied by means of the infusion of methanolic solutions containing the compounds under assay, and using an atmospheric pressure chemical ionization (APCI) as ion source. The MSn spectra obtained for compounds included in the same family, either aminoimidazoazaarenes (AIAs) or carbolines, were compared in order to propose fragmentation pathways for each HA. Moreover, labelled AIAs were used to establish the mechanisms. The protonated molecule was always obtained, but subsequent fragmentation was different for both families. In the case of AIAs, major product ions came from the fragmentation of the aminoimidazole moiety, thus the base peak in MS2 corresponded to the loss of the methyl group, and losses of C2NH3 and CN2H2 were also observed. Further fragmentation occurred in the heterocyclic rings, mainly with losses of HCN and CH3CN. For carbolines, the most important product ions came from the loss of ammonia, except for harman and norharman, the loss of a methyl group for methylated carbolines or the loss of diverse fragments from the heterocyclic rings. In some cases, ion–molecule reactions into the ion trap were observed. For instance, for AαC or MeAαC one ion originating from these reactions corresponded to the base peak. Copyright © 2002 John Wiley & Sons, Ltd.
Lactone enol cation‐radicals: gas‐phase generation, structure, energetics, and reactivity of the ionized enol of butane‐4‐lactone
Authors: Tureček František , Vivekananda Shetty , Sadílek Martin , Polášek Miroslav
Published: September 2002

The cation‐radical of 2‐hydroxyoxol‐2‐ene (1+·) represents the first lactone enol ion whose structure and gas‐phase ion chemistry have been studied by experiment and theory. Ion 1+· was generated by the McLafferty rearrangement in ionized 2‐acetylbutane‐4‐lactone and characterized by accurate mass measurements, isotope labeling, metastable ion and collisionally activated dissociation (CAD) spectra. Metastable 1+· undergoes competitive losses of H‐4 and CO that show interesting deuterium and 13C isotope effects. The elimination of CO from metastable 1+· shows a bimodal distribution of kinetic energy release and produces ·CH2CH2CHOH+ (14+·) and CH3CHCHOH+· (15+·) in ratios which are subject to deuterium isotope effects. Ab initio calculations at the G2(MP2) level of theory show that 1+· is 105 kJ mol−1 more stable than its oxo form, [butane‐4‐lactone]+·(2+·). The elimination of CO from 1+· involves multiple isomerizations by hydrogen migrations and proceeds through ion–molecule complexes of CO with 14+· and 15+·. In addition, CO is calculated to catalyze an exothermic isomerization 14+· → 15+· in the ion–molecule complexes. Multiple consecutive hydrogen migrations in metastable 1+·, as modeled by RRKM calculations on the G2(MP2) potential energy surface, explain the unusual deuterium kinetic isotope effects on the CO elimination. Copyright © 2002 John Wiley & Sons, Ltd.
Determination of ivermectin B1a in animal plasma by liquid chromatography combined with electrospray ionization mass spectrometry
Authors: Croubels S. , De Baere S. , Cherlet M. , De Backer P.
Published: September 2002

A novel, sensitive and specific method for the quantitative determination of ivermectin B1a in animal plasma using liquid chromatography combined with positive electrospray ionization tandem mass spectrometry (LC/ESI‐MS/MS) is presented. Abamectin was used as the internal standard. Extraction of the samples was performed with a deproteinization step using acetonitrile. Chromatographic separation was achieved on a Nucleosil ODS 5 µm column, using gradient elution with 0.2% (v/v) acetic acid in water and 0.2% (v/v) acetic acid in acetonitrile. The method was validated according to the requirements defined by the European Community. Calibration curves using plasma fortified between 1 and 100 ng ml−1 showed a good linear correlation (r ≥ 0.9989, goodness‐of‐fit coefficient ≤8.1%). The trueness at 2 and 25 ng ml−1 (n = 6) was +4.2 and −17.1%, respectively. The trueness and between‐run precision for the analysis of quality control samples at 25 ng ml−1 was −4.0 and 11.0%, respectively (n = 16). The limit of quantification of the method was 1.0 ng ml−1, for which the trueness and precision also fell within acceptable limits. Using a signal‐to‐noise ratio of 3 : 1, the limit of detection was calculated to be 0.2 ng ml−1. The specificity was demonstrated with respect to ivermectin B1b.

The method was successfully used for the quantitative determination of ivermectin B1a in plasma samples from treated bovines, demonstrating the usefulness of the developed method for application in the field of pharmacokinetics. Copyright © 2002 John Wiley & Sons, Ltd.
New results on the dissociative photoionization of CF4 and CCl4
Authors: Kinugawa T. , Hikosaka Y. , Hodgekins A. M. , Eland J. H. D.
Published: September 2002

Using the VIPCO technique, we remeasured and completed the breakdown diagram of CCl4+ up to 21 eV energy. The angle‐resolved data show both orientation and alignment of photoelectrons relative to CX3+ fragments from photoionization to the low‐lying states of CF4+ and CCl4+. The strength of the orientation (forward/backward asymmetry) is surprising in view of the nearly spherical symmetry of the parent molecules, and calls for theoretical explanation. It may indicate that nuclear and electron motion take place on similar time‐scales. Copyright © 2002 John Wiley & Sons, Ltd.
A quantitative model of ultraviolet matrix‐assisted laser desorption/ionization
Authors: Knochenmuss R.
Published: September 2002

A quantitative model of primary ionization in ultraviolet matrix‐assisted laser desorption/ionization (UV‐MALDI) is presented. It includes not only photochemical processes such as exciton pooling, but also the effects of the desorption event. The interplay of these two is found to be a crucial aspect of the MALDI process. The desorbing plume is modeled as an adiabatic expansion with entrained clusters. The parameters in the model are defined as much as possible via experiment or by analogy with known effects. The model was applied to the matrix 2,5‐dihydroxybenzoic acid and found to reproduce the fluence dependence of the fluorescence yield and key features of the picosecond two‐pulse ion generation efficiency curves. In addition, the model correctly predicts a fluence rather than irradiance threshold, the magnitude of the threshold, the magnitude of the ion yield, laser wavelength effects, plume temperatures, plume expansion velocities and the spot size effect. Copyright © 2002 John Wiley & Sons, Ltd.
Long‐term lithium treatment prevents neurotoxic effects of β‐bungarotoxin in primary cultured neurons
Authors: Tseng Wen‐Pei , Lin‐Shiau Shoei‐Yn
Published: September 2002

Lithium is the most commonly used drug for the treatment of manic‐depressive illness. The precise mechanisms underlying its clinical efficacy remain unknown. In this study, we found that long‐term exposure to lithium chloride protected cultured cerebellar granule neurons (CGNs) against β‐bungarotoxin (β‐BuTX)‐induced neurotoxicity. This neuroprotection was exhibited at the therapeutically relevant concentration of 1.2 mM lithium. Pretreatments for 3–5 days (long‐term) were required for protection to occur; but a 3 hr treatment (short‐term) was ineffective. In contrast, a longer treatment for 6–7 days or a higher concentration of 3 mM lithium led not only to loss of the neuroprotective effect but also to a neurotoxic effect. These findings suggest that lithium protection is limited to its narrow window of concentration and apparently relevant to its narrow therapeutic index in clinical application. Measurement of intracellular calcium [Ca2+]i revealed that neurotoxic concentrations of β‐BuTX markedly increased [Ca2+]i, which could be attenuated by long‐term, but not short‐term, lithium treatment. Thus, the protection induced by lithium in CGNs was attributed to its inhibition of calcium overload. In addition, the Ca2+ signaling pathway, including reactive oxygen species production and mitochondrial membrane potential reduction, along with the neurotoxic effect of β‐BuTX was blocked by long‐term, but not short‐term, lithium treatment. All of these results indicate that a crucial step for lithium protection is modulation of [Ca2+]i homeostasis and that lithium neurotoxicity possibly, at least in part, is due to calcium overload. In conclusion, our results suggest that lithium, in addition to its use in treatment of bipolar depressive illness, may have an expanded use in intervention for neurotoxicity. © 2002 Wiley‐Liss, Inc.
Two separate domains in the golli myelin basic proteins are responsible for nuclear targeting and process extension in transfected cells
Authors: Reyes Samuel D. , Campagnoni Anthony T.
Published: September 2002

The golli products of the myelin basic protein (MBP) gene are expressed in neurons and oligodendrocytes (OLs). In certain neuronal populations, golli proteins undergo translocation between the nucleus and cytoplasm/processes during development. The proteins consist of two domains, a golli domain of 133 amino acids and an MBP domain of variable length. One objective of this study was to identify the sequences responsible for nuclear targeting. Site‐directed mutagenesis and deletion analyses were used to generate a series of golli‐green fluorescent protein (GFP) DNA constructs that were transfected into OL and neuronal cell lines to follow localization by confocal microscopy. The results indicated that a 36‐residue stretch in the MBP domain is essential for nuclear targeting, and the sequence appears to be a nontraditional localization signal motif. The studies also revealed that overexpression of golli proteins could induce dramatic changes in cell morphology. In OL lines, overexpression of intact golli proteins, or golli peptide alone, caused an increase in the length and number of processes, and the elaboration of membrane sheets. In the neuronal lines, there was a dramatic increase in number and length of extensions. The results, consistent with the timing of golli expression in cells during neural development, suggest that golli proteins may be involved in process formation/extension in OLs and neurons during development. These studies have defined two functional domains in the golli protein. Sequences in the MBP domain target the protein into the nucleus and sequences within the golli domain induce process sheet extension in OLs and neurons. © 2002 Wiley‐Liss, Inc.
Postnatal development of 11β‐hydroxysteroid dehydrogenase type 1 in the rat hippocampus
Authors: Wan S.L. , Liao M.Y. , Sun K.
Published: September 2002

Glucocorticoids (GCs) have important actions in the hippocampus of the brain, where their access to glucocorticoid receptor (GR) is increased by 11β‐hydroxysteroid dehydrogenase type 1 (11β‐HSD1). 11β‐HSD1 converts biologically inactive 11‐dehydrocorticosterone into active corticosterone. However, the postnatal development of 11β‐HSD1 in the hippocampus is not properly understood. In this study, the postnatal distribution and development of 11β‐HSD1 in the hippocampus of the rat brain was studied with immunohistochemistry and Western blot analysis. Results showed that abundant 11β‐HSD1 immunoreactive substance (ir‐11β‐HSD1) was present in the hippocampus. There were homogeneous distributions of 11β‐HSD1 in the hippocampal CA1, CA2, CA3, CA4 regions and the dentate gyrus at postnatal days 1, 3, and 7. Interestingly, the developmental distribution of GR in the hippocampus followed the same pattern as 11β‐HSD1. Western blot analysis demonstrated that a higher level of expression of 11β‐HSD1 in the hippocampus was found in the first 2 weeks of life. The expressions of 11β‐HSD1 started to drop to adult levels at about postnatal day 15 both in the hippocampus and in other brain areas. These results suggest that the higher expression of 11β‐HSD1 in the neonatal hippocampus may be important for the maturation of the central nervous system mediated by GCs through GR. © 2002 Wiley‐Liss, Inc.
Paradigm shifts in Alzheimer's disease and other neurodegenerative disorders: The emerging role of oligomeric assemblies
Authors: Kirkitadze Marina D. , Bitan Gal , Teplow David B.
Published: September 2002

Alzheimer's disease (AD) is a progressive, neurodegenerative disorder characterized by amyloid deposition in the cerebral neuropil and vasculature. These amyloid deposits comprise predominantly fragments and full‐length (40 or 42 residue) forms of the amyloid β‐protein (Aβ) organized into fibrillar assemblies. Compelling evidence indicates that factors that increase overall Aβ production or the ratio of longer to shorter forms, or which facilitate deposition or inhibit elimination of amyloid deposits, cause AD or are risk factors for the disease. In vitro studies have demonstrated that fibrillar Aβ has potent neurotoxic effects on cultured neurons. In vivo experiments in non‐human primates have demonstrated that Aβ fibrils directly cause pathologic changes, including tau hyperphosphorylation. In concert with histologic studies revealing a lack of tissue injury in areas of the neuropil in which non‐fibrillar deposits were found, these data suggested that fibril assembly was a prerequisite for Aβ‐mediated neurotoxicity in vivo. Recently, however, both in vitro and in vivo studies have revealed that soluble, oligomeric forms of Aβ also have potent neurotoxic activities, and in fact, may be the proximate effectors of the neuronal injury and death occurring in AD. A paradigm shift is thus emerging that necessitates the reevaluation of the relative importance of polymeric (fibrillar) vs. oligomeric assemblies in the pathobiology of AD. In addition to AD, an increasing number of neurodegenerative disorders, including Parkinson's disease, familial British dementia, familial amyloid polyneuropathy, amyotrophic lateral sclerosis, and prion diseases, are associated with abnormal protein assembly processes. The archetypal features of the assembly‐dependent neuropathogenetic effects of Aβ may thus be of relevance not only to AD but to these other disorders as well. © 2002 Wiley‐Liss, Inc.
Interferon‐γ acutely induces calcium influx in human microglia
Authors: Franciosi Sonia , Choi Hyun B. , Kim Seung U. , McLarnon James G.
Published: September 2002

The acute actions of the cytokine, interferon‐γ (IFN‐γ), on intracellular calcium [Ca2+]i levels in human microglia were investigated. In the presence of a calcium‐containing physiological solution (Ca2+‐PSS), IFN‐γ caused a progressive increase in [Ca2+]i to a plateau level with a mean rate of increase of 0.81 ± 0.17 nM/s and mean amplitude of 102 ± 12 nM (n = 67 cells). Washout of the cytokine did not alter the plateau established with IFN‐γ in Ca2+‐PSS; however, introduction of a Ca2+‐free PSS diminished [Ca2+]i to baseline levels. The decrease in [Ca2+]i with Ca2+‐free PSS would indicate that the response to IFN‐γ was mediated by an influx pathway. This result was confirmed in separate experiments showing the lack of an induced change in [Ca2+]i with IFN‐γ applied in Ca2+‐free PSS. The increase in [Ca2+]i induced in Ca2+‐PSS was reduced to near baseline levels when the external solution contained low Cl− in the maintained presence of IFN‐γ suggesting that cellular depolarization inhibited the cytokine mediated entry pathway. The compound SKF96365, which blocks store operated influx of Ca2+ in human microglia, was ineffective in altering the increase in [Ca2+]i, however, La3+ completely inhibited the Ca2+ response induced by IFN‐γ. Whole‐cell patch clamp studies showed no effect of IFN‐γ to alter outward currents and inward rectifier K+ currents. The influx of Ca2+ may serve a signaling role in microglia linking IFN‐γ to functional responses of the cells to infiltrating T lymphocytes into the central nervous system (CNS) during inflammatory processes. © 2002 Wiley‐Liss, Inc.
Metabolic changes in the cerebrospinal fluid of patients with lumbar disc herniation or spinal stenosis
Authors: Gårseth Mari , Sonnewald Ursula , White Linda R. , Rød Marianne , Nygaard Øystein , Zwart John‐Anker
Published: September 2002

Metabolite levels in cerebrospinal fluid from patients with lower back pain and/or sciatica caused by disc herniation or spinal stenosis were compared with levels in pain‐free controls using proton magnetic resonance spectroscopy. Significant differences for several metabolites were found in patients with pain compared with controls. Most changes were found in the group with disc herniation, including reductions in glucose, alanine, and lactate, suggesting increased aerobic metabolism in this group. There was a significant reduction in the level of glucose in the group with spinal stenosis irrespective of whether the patients were compared with the whole control group (age‐weighted) or with age‐matched controls. Additionally, inositol and creatinine were reduced in patients with disc herniation. Inositol was also significantly reduced in the spinal stenosis group when age matched to controls. Insofar as the levels of pain recorded by the patients with lumbar pathology were similar in the two groups, it seems more likely that the reductions in metabolite levels recorded in the group with disc herniations are related to disc pathology rather than the perception of pain. However, the possibility that pain perception contributes to the metabolic changes cannot be excluded. © 2002 Wiley‐Liss, Inc.
Gene transfer of glial cell‐derived neurotrophic factor and cardiotrophin‐1 protects PC12 cells from injury: Involvement of the phosphatidylinositol 3‐kinase and mitogen‐activated protein kinase kinase pathways
Authors: Toth Gabor , Yang Huibin , Anguelov Roumen A. , Vettraino Jason , Wang Yuying , Acsadi Gyula
Published: September 2002

Gene therapy for neurodegenerative diseases may utilize the expression of neurotrophic factors because of their potential to promote survival and regeneration of injured neuronal cells. Increasing numbers of these factors are being considered for gene transfer, but their specificity and efficacy in neuroprotection are greatly variable. The major aims of this study were to carry out gene transfer of various neurotrophic factors and investigate their mechanisms of action as well as their protective effects on the viability of rat pheochromocytoma (PC12) cells. We used glutamate, S‐nitroso‐N‐acetyl‐DL‐penicillamine (SNAP), and staurosporine to induce excitatory damage, oxidative stress, and apoptosis, respectively, because these mechanisms are thought to participate in various disease processes leading to degeneration of cells. We utilized adenovirus vectors for efficient gene transfer of trophic factors (glial‐cell derived neurotrophic factor [GDNF] and cardiotrophin‐1 [CT‐1]) or calbindin‐D28k. We found that GDNF and CT‐1 gene transfers were equally effective in saving PC12 cells from injury, but calbindin expression did not show any beneficial effects. GDNF gene transfer was much more efficient in protecting PC12 cells from damage than direct GDNF administration. The protection by GDNF expression against staurosporine was mediated through both phosphatidylinositol 3‐kinase (PI3K) and mitogen‐activated protein kinase kinase (MAPK kinase; MEK) pathways, but only the MEK pathway was involved in the protection against SNAP. In contrast, the protective effect of GDNF against glutamate toxicity was independent of these RET‐dependent signal transduction pathways. © 2002 Wiley‐Liss, Inc.
Is abdominoperineal resection a good option for stage IV adenocarcinoma of the distal rectum?
Authors: Chu Quyen D. , Davidson Robert S. , Rodriguez‐Bigas Miguel A. , Wirtzfeld Debrah A. , Petrelli Nicholas J.
Published: September 2002

Background and Objectives

The management of the primary lesion in patients with stage IV adenocarcinoma of the distal rectum is controversial. An abdominoperineal resection (APR) may be a good option.

Methods

A retrospective analysis of the medical records of 21 patients with stage IV distal rectal adenocarcinoma treated with an APR between January 1991 to December 2000 was performed.

Results

All patients had an Eastern Cooperative Oncology Group (ECOG) performance status of 1 and normal preoperative alkaline phosphatase and total bilirubin levels. Twelve patients (92%) with liver metastases had less than 25% of total liver volume involvement. Twenty patients (95%) had complete resolution of their symptoms related to the primary rectal cancer. The median follow‐up was 19 months (range 3–92 months), with a median survival of 21.6 months and a 2‐year overall survival of 34%.

Conclusions

Patients with stage IV distal rectal adenocarcinoma who have a good performance status, normal preoperative liver function tests, and minimal metastatic disease to the liver can be offered resective surgery. J. Surg. Oncol. 2002;81:3–7. © 2002 Wiley‐Liss, Inc.
Postoperative morbidity, mortality, and survival in lung cancer associated with idiopathic pulmonary fibrosis
Authors: Kawasaki Hidenori , Nagai Kanji , Yoshida Junji , Nishimura Mitsuyo , Nishiwaki Yutaka
Published: September 2002

Background

Although postoperative morbidity and mortality rates in patients with lung cancer have decreased with advances in perioperative management, those patients with idiopathic pulmonary fibrosis (IPF) remain at a high risk of complication and death. The frequency of postoperative morbidity and mortality rates in patients with lung cancer who have IPF have seldom been reported, however.

Methods

A retrospective study of 711 patients with lung cancer who had undergone surgical resection was conducted. Medical records were retrospectively compared for factors that might affect postoperative morbidity and mortality in patients with and without IPF.

Results

Of the 711 patients with lung cancer, 53 (7.5%) had IPF. The patients with IPF had pulmonary morbidity and mortality more frequently than those without IPF (26% versus 9.1%, P < 0.01; 8% versus 0.8%; P < 0.01). The 5‐year survival was 43% among patients with IPF and 64.2% among those without IPF. Overall survival in patients with IPF was significantly lower than in those without IPF (P < 0.01), but disease‐free survival was similar in the groups. Thirty‐five percent of the deaths (8 of 23) were not related to lung cancer in those patients with IPF, compared with 18% (35 of 199) of the deaths among those without IPF (P = 0.048).

Conclusion

Patients with IPF showed markedly higher postoperative pulmonary morbidity and mortality than those without IPF. The survival rate of patients with IPF was lower because of pulmonary complications. Careful preoperative evaluation and perioperative management are required to achieve optimal surgical outcome in patients with lung cancer who have IPF. J. Surg. Oncol. 2002;81:33–37. © 2002 Wiley‐Liss, Inc.
Biologic and imaging diagnosis of lymph node metastasis in esophageal carcinoma
Authors: Natsugoe Shoji , Nakashima Saburo , Matsumoto Masataka , Sakita Hironori , Sakamoto Fuminori , Okumura Hiroshi , Baba Masamichi , Yoshinaka Heiji , Takao Sonshin , Aikou Takashi
Published: September 2002

Background and Objectives

Few reports have described the combined use of biologic and imaging techniques in the diagnosis of lymph node metastasis. We prospectively evaluated lymph node metastasis diagnosed by biologic and imaging means in patients with esophageal carcinoma.

Methods

Preoperative ultrasound and endoscopic ultrasound (EUS) examination were performed in 80 patients. Biopsy specimens were immunohistochemically examined using cyclin D1 (CD1) and desmoglein 1 (DG1) antibodies, and tumors were classified into three grades.

Results

The sensitivity, specificity, and accuracy values of ultrasound examination were 88.2, 58.6, and 77.5%, respectively. The incidence of nodal involvement was 0% (0/10) in patients with grade 1 tumors, 57.1% (16/28) in those with grade 2 tumors, and 83.3% (35/42) in those with grade 3 tumors. Of the 57 patients with lymph node metastasis determined sonographically, 50 had grade 2 or 3 tumors that were histologically confirmed. The remaining seven patients with grade 1 tumors did not have involved nodes. Of the 23 patients without lymph node metastasis according to ultrasound examination, the incidence of lymph node metastasis in patients with grade 1, 2, and 3 tumors was 0, 16.7, and 50.0%, respectively.

Conclusions

When used together, imaging and molecular procedures may offer improved identification of lymph node metastasis in patients with squamous cell carcinoma of the esophagus. J. Surg. Oncol. 2002;81:25–32. © 2002 Wiley‐Liss, Inc.
Solvent and structural effects on the oxidation of 2,6‐diphenyl‐piperidin‐4‐ones by quinolinium chlorochromate
Authors: Saravana Kanna S. , Elango K. P.
Published: September 2002

The kinetics of oxidation of 3‐R‐2,6‐diphenyl‐piperidin‐4‐ones (where R = H, Me, Et, and i‐Pr) by quinolinium chlorochromate has been studied under pseudo‐first‐order conditions in different pure (protic and aprotic) solvents. The rate data is correlated with different solvent parameters using linear multiple regression analysis. From the regression coefficients, information on the solvent–reactant and the solvent–transition state interactions is obtained and the solvation models are proposed. Reasons for the difference in reactivity with structure are also discussed. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 585–588, 2002
Oxidation of indole‐3‐acetic acid by peroxomonosulphate: A kinetic and mechanistic study
Authors: Chandramohan G. , Kalyanasundharam S. , Renganathan R.
Published: September 2002

Kinetics of oxidation of indole‐3‐acetic acid (IAA) by peroxomonosulphate (PMS) in aqueous acetonitrile medium has been investigated. The reaction follows a total second order, first order each with respect to [IAA] and [PMS]. The rate of the reaction was not affected by added [H+]. Variation of ionic strength (μ) had no influence on the rate. Increase of percentage of acetonitrile decreased the rate. Absence of any polymerization indicated a nonradical pathway. Activation and thermodynamic parameters have been computed. A suitable kinetic scheme based on these observations is proposed. The reactivity of PMS towards IAA was found to be higher than that with peroxodisulphate. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 569–574, 2002
Kinetics of base hydrolysis of novel low spin Fe(II) amino acid Schiff base chelates—hydrophobic structural effects
Authors: Shaker Ali M. , Nassr Lobna A. E.
Published: September 2002

The reactivity against OH− ion of some novel Fe(II) complexes of Schiff base ligands derived from salicylaldehyde or o‐hydroxynaphth‐aldehyde and some variety of amino acids has been examined in aqueous and aqua‐ethanol mixtures. The rate law and relevant mechanism were assumed. Base hydrolysis kinetics measurements revealed pseudo‐first‐order doubly stage rates because of the presence of mer‐ and fac‐isomers. The evaluated rate constants and activation parameters are consistent with the stability constants of the investigated complexes. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 595–602, 2002
Involvement of both extracellular signal‐regulated kinase and c‐jun N‐terminal kinase pathways in the 12‐O‐tetradecanoylphorbol‐13‐acetate–induced upregulation of p21Cip1 in colon cancer cells
Authors: Lin Shyr‐Yi , Liang Yu‐Chih , Ho Yuan‐Soon , Tsai Shu‐Huei , Pan Shiann , Lee Wen‐Sen
Published: September 2002

Protein kinase C (PKC), a family of serine‐threonine kinases, has been implicated in the regulation of colon tumorigenesis. However, the specific isoform of PKC involved in this process is not clear. In the present study, we found that treatment of the cultured human colon cancer cell line COLO‐205 with a PKC agonist, 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA), resulted in cell‐cycle arrest at the G0/G1 phase, decrease in cell number, PKCγ isoform translocation, and upregulation of p21Cip1 protein. Pretreatment of the cells with a PKC inhibitor, staurosporine, prevented the TPA‐induced upregulation of p21Cip1 protein. Based on the findings of the present study including that (a) both extracellular signal‐regulated kinase (ERK) and c‐jun N‐terminal kinase (JNK) were activated in the TPA‐treated COLO‐205 cells, (b) pretreatment with the mitogen‐activated protein kinase kinase inhibitor PD98059 but not with the p38 mitogen‐activated protein kinase inhibitor SB203580 blocked the TPA‐induced p21Cip1 in COLO‐205 cells, and (c) transient transfection of the COLO‐205 cells with dominant negative ERK or JNK plasmid significantly suppressed the TPA‐induced p21Cip1 protein induction, we conclude that both the ERK and JNK pathways are involved in the TPA‐induced upregulation of p21Cip1 protein in the COLO‐205 cells. © 2002 Wiley‐Liss, Inc.
Inducible expression of the gap junction protein connexin43 decreases the neoplastic potential of HT‐1080 human fibrosarcoma cells in vitro and in vivo
Authors: King Timothy J. , Fukushima Laurie H. , Yasui Yutaka , Lampe Paul D. , Bertram John S.
Published: September 2002

Numerous studies have demonstrated a correlation between dysregulation/loss of connexin expression or gap junction intercellular communication (GJIC) function and decreased growth control both in human tumors and tumor cell lines. Likewise, restoration of constitutive connexin expression/function is correlated with increased growth control/decreased tumorigenicity. Here, we show for the first time that inducible restoration of connexin43 (Cx43) expression and GJIC function in a human tumor line of mesenchymal origin (HT‐1080, fibrosarcoma) resulted in a lowered neoplastic potential. Specifically, HT‐1080 cells induced to express Cx43 demonstrated diminished foci formation when in co‐culture with normal fibroblasts, decreased colony formation under anchorage‐independent conditions, and reduced tumor growth when injected into immunodeficient mice. These results, obtained utilizing an inducible system that helps address issues of clonal heterogeneity, strongly implicate Cx43 as a tumor suppressor in human tissue of mesenchymal origin and GJIC as a regulatory mechanism for cellular growth control both in vitro and in vivo. This study also further supports the hypothesis that loss of Cx43/GJIC in human tumors may play an important role in the dysregulation of normal growth control. © 2002 Wiley‐Liss, Inc.
Economics and operations management: towards a theory of endogenous production speed
Authors: Powell Philip T. , Schmenner Roger W.
Published: September 2002

A firm chooses the production speed and amount of labor that maximizes profit in a perfectly competitive market. Faster production raises management expenses and the unit cost of production mistakes. Adding workers enhances the division of labor on the production line and raises work‐in‐process inventory. When the division of labor is high, a rise in the wage can increase the optimal production speed and quantity of output. When price falls, optimal production speed and optimal division of labor can move in opposite directions. Output quantity can also rise, generating a downward sloping supply curve in the absence of increasing returns to scale. Copyright © 2002 John Wiley & Sons, Ltd.
What makes a blockbuster? Economic analysis of film success in the United Kingdom
Authors: Collins Alan , Hand Chris , Snell Martin C.
Published: September 2002

In this paper, we attempt to evaluate whether a film's commercial performance can be forecast. The statistical distribution of film revenues in the UK is examined and found to have unbounded variance. This undermines much of the existing work relating a film's performance to its identifiable attributes within an OLS model. We adopt De Vany and Walls' approach and transform the revenue data into a binary variable and estimate the probability that a film's revenue will exceed a given threshold value; in other words, the probability of a blockbuster. Furthermore, we provide a sensitivity analysis around these threshold values. Copyright © 2002 John Wiley & Sons, Ltd.
Outlet ownership in franchising systems: an agency based approach
Authors: Seshadri Sudhindra
Published: September 2002

Building on prior agency theoretic explanations of the franchisor–franchisee relationship, this paper introduces the franchise system manager in the traditional dyadic channel. This allows us to link the franchisors internal agency problems of providing incentives to managers to their external agency problems of acquiring and extracting rents from franchisees. I find preliminary empirical support for this approach in a structural equations model estimated on a franchise system data set. I then develop and analyze an agency‐theoretic model with agency tradeoffs. An explicit rationale for mixed ownership in franchising emerges from the model, where the share of company owned outlets is endogenously determined as the tradeoff between franchisee rents and managerial compensation. Copyright © 2002 John Wiley & Sons, Ltd.
On singular mono‐energetic transport equations in slab geometry
Authors: Chabi Mohamed , Latrach Khalid
Published: September 2002

In this paper we establish the well posedness of the Cauchy problem associated to transport equations with singular cross‐sections (i.e. unbounded collisions frequencies and unbounded collision operators) in L1 spaces for specular reflecting boundary conditions. In addition, we discuss the weak compactness of the second‐order remainder term of the Dyson–Phillips expansion. This allows us to estimate the essential type of the transport semigroup from which the asymptotic behaviour of the solution is derived. The case of singular transport equations with periodic boundary conditions is also discussed. The proofs make use of the Miyadera perturbation theory of positive semigroups on AL‐spaces. Copyright © 2002 John Wiley & Sons, Ltd.
Design of double‐balanced MMIC mixer for Ka‐band satellite communications
Authors: Ryu Keun‐Kwan , Jang Dong‐Phil , Lee Moon‐Que , Yom In‐Bok , Lee Seong‐Pal
Published: September 2002

A MMIC (monolithic microwave integrated circuit) mixer chip using the Schottky diode of an InGaAs/GaAs p‐HEMT process has been developed to act as the receiver down converter of a Ka‐band satellite transponder. A different approach to the MMIC mixer structure is applied for reducing the chip size by the exchange of ports between IF and LO. This MMIC covers with RF (30.6–31.0 GHz) and IF (20.8–21.2 GHz). According to the on‐wafer measurement, the miniature (3.0 × 1.5 mm) MMIC mixer demonstrates conversion loss below 7.8 dB, LO‐to‐RF isolation above 27 dB, LO‐to‐IF isolation above 19 dB, and RF‐to‐IF isolation above 40 dB, respectively. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 401–403, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10475
Propagation characteristics of suspended MIS coupled slow‐wave microstrip lines
Authors: Verma A. K. , Nasimuddin  , Sharma Enakshi K.
Published: September 2002

The single‐layer reduction (SLR) formulation is presented to compute the propagation characteristics, that is, the slowing factor (normalized phase constant) and the attenuation constant of the even and odd modes of the suspended MIS coupled slow‐wave microstrip lines. The proposed structure is suitable for the design of a compact high‐directivity coupler. For the standard coupled MIS microstrip line the SLR computes the slowing factor with deviation about 1% and the attenuation constant with 0.005 dB/mm difference against reults of the spectral domain analysis (SDA). The SLR is as accurate as the SDA; however, computationally it is much faster than the SDA. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 403–405, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10476
Very‐low‐profile bent planar monopole antenna for GSM/DCS dual‐band mobile phone
Authors: Lee Gwo‐Yun , Wong Kin‐Lu
Published: September 2002

By inserting several slits into a rectangular planar monopole, which meanders the monopole, and further bending it into two equal and perpendicular sections, a novel very‐low‐profile monopole antenna for applications in GSM/DCS dual‐band mobile phones is presented. The antenna height is only 7 mm (about 2.1% of the wavelength at 900 MHz) from the ground plane, and the obtained impedance bandwidths cover the required operating bandwidths of the GSM (890–960 MHz) and DCS (1710–1880 MHz) bands. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 406–409, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10477
Design of microstrip reflect array using data from isolated patch analysis
Authors: Venneri F. , Angiulli G. , Di Massa G.
Published: September 2002

The design of microstrip reflect arrays requires the use of a design curve to correlate the phase of the reradiated field and the size of the elements. In this Letter this parameter has been evaluated by analyzing the field scattered from an isolated reflect‐array unit cell. As a test case a microstrip reflect array has been designed with the use of these data. Even if this approach neglects the mutual coupling effects, the measured reflect‐array radiation pattern shows that the main beam steering agrees with the design requirements. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 411–414, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10479
An algebraic domain decomposition algorithm for the vector finite‐element analysis of 3D electromagnetic field problems
Authors: Chen R. S. , Yung Edward K. N. , Chan C. H. , Wang D. X. , Jin J. M.
Published: September 2002

This Letter, proposes an algebraic domain decomposition algorithm (ADDA) to solve large sparse linear systems derived from the vector finite‐element method (FEM) for 3D electromagnetic field problems. The proposed method segments the problem into several smaller pieces, solves each subproblem by direct methods, and then reassembles the subproblem solutions together to get the global result. Block LU factorization and multifrontal method are applied to solve each subproblem for the generation of the reduced system, and iterative methods are applied to solve the reduced system. It is shown that if combined with ADDA, biconjugate gradient method (BCG) converges more rapidly than the conjugate gradient method (CG), and both of them are faster than the conventional CG method. The simulation results demonstrate that the proposed algorithm can efficiently solve large and sparse linear equations arising from the finite‐element method for the electromagnetic problems involving complex media such as perfectly matched layers (PMLs), which often make the linear equation ill‐conditioned. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 414–417, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10480
Numerical analysis of optical waveguides with the use of Fourier‐series expansion method combined with perfectly matched layer
Authors: Yasumoto Kiyotoshi , Watanabe Koki , Ishihara Junya
Published: September 2002

A numerical approach for transition problems in optical waveguides is presented, with the use of the Fourier‐series expansion method combined with the absorbing boundary condition by a perfectly matched layer (PML). The optical propagation along a transition is described by a simple matrix algebra. The numerical examples demonstrate that the radiation modes with wider propagation angle are strongly attenuated in the presence of PML, and hence unwanted interference of the boundary‐reflected radiation field to the guided wave field is suppressed. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 422–426, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10482
Large‐signal modeling of frequency‐dispersion effects in submicron MOSFET devices
Authors: Toner B. , Fusco V. F.
Published: September 2002

In this Letter a large‐signal model for the MOSFET will be presented, along with the parameter extraction for the model using large‐signal time‐domain waveforms. The dc/ac hybrid model described accounts for the discrepancy between dc and large‐signal rf extracted equivalent circuit conductance and transconductance parameters. In addition, the dynamic nature of the modeling process directly characterizes other phenomena associated with high‐power operation such as self‐heating effects. Full verification of the model is provided for an 80 μm/0.18 μm MOSFET. An improvement in the performance of the model over traditional quasi‐static models at rf whilst maintaining the accuracy of the dc model is demonstrated. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 429–432, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10485
On the influence of electron‐beam parameters on TWT small‐signal gain
Authors: D'Agostino Stefano , Paoloni Claudio
Published: September 2002

The electron beam is one of the main components in traveling‐wave tubes (TWTs). A study on the influence of the parameters related to the electron beam on small‐signal gain of TWTs is proposed. In particular, the effect of the variations of electron‐beam voltage, the perveance of the electron gun, and electron beam radius are investigated. A five‐section TWT was considered in the study. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 433–434, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10486
Fast analysis of scattering by arbitrarily shaped three‐dimensional objects using the precorrected‐FFT method
Authors: Nie Xiaochun , Li Le‐Wei , Yuan Ning , Yeo Tat Soon
Published: September 2002

This Letter presents a fast solution to the electric‐field integral equation (EFIE) for large, three‐dimensional, arbitrarily shaped objects. The EFIE is discretized by the method of moments and the precorrected‐FFT method is then used to accelerate the matrix–vector multiplications in iterations. The resulting algorithm leads to a great reduction in memory requirement and execution time and can be modified to fit a wide variety of systems with different Green's functions without excessive effort. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 438–442, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10488
A dual‐band bidirectional multilevel monopole antenna
Authors: Soler Jordi , Puente Carles , Puerto Alberto
Published: September 2002

A dual‐band monopole antenna that permits tailoring the shape of the radiation patterns to provide bidirectional coverage is presented. The antenna provides an optimum input return loss and could be used in those applications where a bidirectional pattern is required. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 445–448, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10490
An extension of the two‐slot radiation model to stacked patches with infinite and finite ground plane
Authors: Rajo‐Iglesias Eva , Vázquez‐Roy José‐Luis , Segovia‐Vargas Daniel , González‐Posadas Vicente , Martín‐Pascual Carlos
Published: September 2002

This Letter presents a new radiation model for stacked‐patch antennas. The model is based on the two‐slot model and consists of a four‐ or six‐element array, depending on the supposition of infinite ground plane. The parameters that can be extracted from this model, such as coupling coefficient, surface‐wave coefficients, and phases are very useful in stacked‐patch design. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 448–451, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10491
Comparison of 2D particle‐in‐cell simulation with 1D nonlinear theory of helix traveling‐wave tubes
Authors: Jung Sun‐Shin , Soukhov Andrei V. , Park Gun‐Sik
Published: September 2002

Two‐dimensional (2D) particle‐in‐cell (PIC) simulations, using MAGIC code, have been performed for wide‐band helix traveling‐wave tubes (TWTs) in a large‐signal regime. Fundamental and second‐harmonic power calculated over a 1.5‐octave frequency range of 6–18 GHz were compared and found to be in good agreement with those obtained by one‐dimensional (1D) nonlinear theory. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 451–454, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10492
Novel photonic crystal waveguide in microwave printed‐circuit technology
Authors: Falcone Francisco , Lopetegi Txema , Laso Miguel A. G. , Sorolla Mario
Published: September 2002

In this Letter a novel type of waveguide based on a photonic crystal and implemented in microwave printed‐circuit technology is proposed. The novel waveguide is obtained by introducing a line defect in a 2D photonic crystal placed inside a parallel‐plate waveguide. The resulting structure supports guided modes that propagate along the line defect. Simulation and measurement results confirming the existence of a low‐loss waveguiding band are presented. The novel type of planar waveguide has a quasi‐TEM fundamental mode and is compatible with the widely employed microstrip technology, but because of its unique configuration it does not suffer from some problems common to planar technologies like radiation losses or surface‐wave mode excitation. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 462–466, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10496
Effects of the adjacent channels on IP3 of RF amplifiers
Authors: Ma Jian‐Guo
Published: September 2002

In this Letter the effects of the adjacent channels on the IP3 and the 1‐dB compression point of a RF amplifier are investigated with the use of a three‐tone test instead of single‐tone and two‐tone tests in the conventional 1‐dB and IP3 investigations. The results show that the 1‐dB point and the IP3 have been lowered because of the adjacent channel signals. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 1–3, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10499
A beam launching method for propagation modeling in multipath contexts
Authors: Tahri R. , Letrou C. , Hanna V. Fouad
Published: September 2002

A new technique for propagation modeling in multipath contexts is proposed as a fast and sufficiently precise alternative to ray‐based techniques. This technique is based on frame decomposition of source fields into a set of Gaussian beams. Its validity is demonstrated in the case of wave propagation in a rectangular metallic waveguide. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 6–10, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10501
Application of a 2D‐CFDTD algorithm to the analysis of photonic crystal fibers (PCFs)
Authors: Zhu Yanjie , Chen Yinchao , Huray Paul , Dong Xiaopeng
Published: September 2002

This research applies an efficient two‐dimensional cylindrical finite‐difference–time‐domain (2D‐CFDTD) algorithm implemented on the transverse plane of a guided‐wave structure to analyze a photonic crystal fiber (PCF) structure. An unsplit anisotropic perfectly matched layer (APML) is used for mesh termination along the radial direction of the PCF. The propagation characteristics of the PCF are analyzed, and excellent agreement is observed between the results derived in this research and those available in the literature. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 10–14, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10502