bluuebunny/crossref_metadata_2025 huggingface dataset:
RQRP protocol for video delivery over IP
Authors: Lee B. S. , Yeo C. K. , Poon S. M. , Song J.
Published: August 2002

The Digital Audio‐Visual Council has adopted the Request/Reply (RQRP) protocol, proposed by one of the authors, for the delivery mechanism of MPEG video streams. In this paper, we investigate the network characteristics of the RQRP protocol and analyse the protocol's performance via both simulation as well as actual experimental results. In this simulation, the RQRP protocol was mathematically an ideal model first and later, a feedback control system. Simulation results showed that, for both models, the network traffic is able to follow the playout rate at the receiver. In the case of the latter, which involves a simpler implementation, oscillation in network traffic is observed. A video‐on‐demand (VoD) system using the RQRP protocol was developed and experiments were performed. The results obtained are consistent with the simulation results. Copyright © 2001 John Wiley & Sons, Ltd.
Level crossing rate and average fade duration for pure selection and threshold selection diversity‐combining systems
Authors: Yacoub M. D. , da Silva C. R. C. M. , Vargas B J. E.
Published: August 2002

Exact and closed‐form expressions for the level crossing rate and average fade duration are presented for the M‐branch Pure Selection Combining and for the two‐branch Threshold Selection Combining schemes, assuming independent branches in a Rayleigh environment. The analytical results are thoroughly validated by reducing the general case to some special cases, for which the solutions are known, and by means of simulation for the more general case. The plots presented here are also compared with those of the general solution recently published for the Equal Gain and Maximal Ratio Combining and an agreeable coherence is found. Copyright © 2001 John Wiley & Sons, Ltd.
Cytodiagnosis of bile microspheroliths: A case report
Authors: Sandmeier D. , Mihaescu A.
Published: August 2002

We recently observed numerous microspheroliths consisting of microscopic organized crystalline structures of varying shapes, sizes, and colors in a bile specimen from a 65‐yr‐old woman obtained directly from the gallbladder during a surgical procedure for cholecystectomy. Detection of microspheroliths could be very useful in the diagnostic approach to patients with recurrent pain in the biliary region or with acute pancreatitis of unknown origin. To date, we are unaware of any cytologic reports describing microspheroliths in bile. Diagn. Cytopathol. 24:247–248, 2001. © 2001 Wiley‐Liss, Inc.
Carcinoma of temporal bone, base of the skull: Diagnosis by needle aspiration cytology
Authors: Zaharopoulos Paul
Published: August 2002

We report on a 68‐yr‐old male with a destructive bone lesion involving the temporal bone at the skull base extending to surrounding osseous structures and the infratemporal fossa, defined by needle aspiration cytology as carcinoma in association with inflammatory reaction, bacterial type, and bone destruction. The technique of the aspiration, which was performed by a cytopathologist directing a spinal needle into the region of the destroyed temporal bone as outlined in the radiographs of prior magnetic resonance imaging (MRI), is discussed. The application of this technique in the cytologic sampling of deeper lesions usually of soft or ossecus tissues not accessible to ordinary fine‐needle aspiration is presented. There is also a brief discussion of neoplastic lesions involving the temporal bone at the skull base and the anatomic concerns in sampling lesions in this difficult‐to‐approach region of the body. Diagn. Cytopathol. 24:356–360, 2001. © 2001 Wiley‐Liss, Inc.
Fine‐needle aspiration diagnosis of medulloblastoma metastatic to the pelvis
Authors: New Kent C. , Bulsara Ketan R. , Dodd Leslie G. , Cummings Thomas J.
Published: August 2002

A 25‐yr‐old male presented with a cerebellar mass, underwent a suboccipital craniotomy, and was diagnosed with medulloblastoma. Six months later he developed a large mass in the right iliac crest. Fine‐needle aspiration biopsy (FNAB) confirmed the diagnosis of metastatic medulloblastoma. The diagnosis of metastatic medulloblastoma is usually suspected clinically or radiographically, and is uncommonly confirmed by cytologic evaluation. Here we report on a rare case of FNAB used to diagnose metastatic medulloblastoma. Diagn. Cytopathol. 24:361–363, 2001. © 2001 Wiley‐Liss, Inc.
Clinical relevance of benign endometrial cells in postmenopausal women
Authors: Ashfaq Raheela , Sharma Suash , Dulley Tara , Saboorian M. Hossein , Siddiqui Momin T. , Warner Claudia
Published: August 2002

Our objective was to determine if the finding of benign endometrial cells on a Papanicolaou (Pap) smear of a postmenopausal woman is associated with endometrial/uterine pathology, independent of symptomatology and hormone replacement therapy (HRT) status. The medical records of 146 postmenopausal patients who had a Pap smear showing normal‐appearing endometrial cells between January 9, 1997 and January 12, 2000 were reviewed. Uterine pathology for each patient was determined by reviewing the results of endometrial sampling (endometrial biopsy or dilatation and curettage), hysterectomy, or pelvic sonogram, which were performed within 24 mo of the cytologic smear. The results were then correlated with clinical symptomatology and HRT status of each patient at the time the cytologic smear was obtained. Of the 146 Pap smears coded with “endometrial cells in a postmenopausal woman,” 50 were excluded due to prior hysterectomy, perimenopausal status, and absence of further follow‐up. Of the remaining 96 women, 27 (28%) had benign pathologic findings including polyps, leiomyomata, and simple hyperplasia without atypia, whereas 11 (12%) had significant pathologic findings including hyperplasia with atypia, adenocarcinoma, mixed Mullerian tumor, and leiomyosarcoma. Of the 11 patients with significant pathology, only one patient did not have abnormal vaginal bleeding but instead had a 30‐wk‐size irregular uterus on examination, and only 2 patients received hormone replacement therapy. In conclusion, Reporting endometrial cells on Pap smears in postmenopausal women did not lead to the diagnosis of any cases of significant pathology that would have gone unsuspected clinically. Moreover, HRT status did not affect the incidence of normal endometrial cells on Pap smears in postmenopausal women, nor did it aid in distinguishing which postmenopausal women had endometrial/uterine pathology. This calls into question the usefulness of the current Bethesda guideline to report “benign endometrial cells in a postmenopausal woman.” Diagn. Cytopathol. 25:235–238, 2001. © 2001 Wiley‐Liss, Inc.
Liesegang rings in a submental mass: Fine‐needle aspiration with histologic correlation
Authors: Pavot Dawn R. , Atkins Kristen A. , Powers Celeste N.
Published: August 2002

Liesegang rings are lamellated concretions commonly found in chronic cystic lesions that are inflamed, necrotic, fibrotic, or hemorrhagic. We report on an unusual case of a 14‐yr‐old girl with an acute, rapidly enlarging solid submental mass in which Liesegang rings were identified on aspirate smears. Diagn. Cytopathol. 25:331–333, 2001. © 2001 Wiley‐Liss, Inc.
Extracellular ATP regulation of airway secretion
Authors: Shimura Sanae
Published: August 2002

Both the superficial epithelium and submucosal glands play a role in airway secretion. Electrophysiological experiments showed that extracellular ATP induced an initial transient increase in Cl– secretion followed by a prolonged inhibition of Na+ absorption in rabbit tracheal epithelium, which lacks submucosal glands. The response to ATP was mimicked by UTP or ATPγS in untreated normal epithelium, suggesting a P2U‐type receptor in the epithelium. Meanwhile, in tracheal epithelium from SO2‐induced bronchitic rabbit ATP induced a prolonged increase in Cl– secretion without a decrease in Na+ absorption, which was mimicked by adenosine or isoproterenol (ISP). The alteration in the bronchitic epithelium was shown to result from a newly expressed CFTR by both immunohistological and Northern blot analysis. Patch‐clamp experiments showed that ATP induced an initial Cl– current followed by K+ current in acinar cells of submucosal glands isolated from feline and human trachea. Although ISP alone or adenosine did not evoke any significant current responses, ISP augmented the ATP‐induced Cl– and K+ currents. A phosphodiesterase inhibitor, 3‐isobutyl‐1‐methylxanthine (IBMX), mimicked the augmentation by ISP. ATP also induced an increase in [Ca2+]i in acinar cells of submucosal glands, which was augmented by ISP. Mucus glycoprotein (MGP) secretion from isolated submucosal glands was also stimulated by ATP but not by adenosine. The ATP‐induced MGP secretion was augmented by ISP. These findings suggest that P2‐receptor stimulation and the resultant [Ca2+]i‐rise induce both electrolyte and MGP secretion, which is enhanced by [cAMP]i‐rise in airway submucosal glands. Drug Dev. Res. 52:170–177, 2001. © 2001 Wiley‐Liss, Inc.
Clinical experience with antithrombotic drugs acting on purine receptor pathways
Authors: Storey Robert F.
Published: August 2002

Rupture of atherosclerotic plaques and subsequent thrombus formation in coronary arteries are key events in the progression of coronary artery disease and the pathogenesis of acute coronary syndromes. Platelets play a crucial role in this thrombus formation and the success of aspirin in reducing cardiovascular morbidity and mortality has spurred on the search for antiplatelet agents that have an alternative mechanism of action and may, therefore, add to the therapeutic effects of aspirin. The thienopyridines, ticlopidine and clopidogrel, act via metabolites on the platelet ADP receptor subtype designated P2T, and these agents have proven clinical efficacy, either as alternatives to aspirin or, in prevention of coronary stent thrombosis, in combination with aspirin. Potent P2T receptor antagonists have been developed that act directly on the receptor and have a rapid onset of action. One such antagonist, AR‐C69931MX, is being developed for clinical use. AR‐C69931MX is a potent antagonist of ADP‐induced platelet activation, aggregation, and secretion and also antagonises platelet responses to all other agonists in view of the central role of the P2T receptor in amplifying platelet responses. Phase II studies of intravenous AR‐C69931MX in patients with acute coronary syndromes show that this agent has a rapid onset of action, rapidly achieving steady‐state inhibition of platelet aggregation, with a half‐life of only a few minutes. AR‐C69931MX appears to be safe and well tolerated as adjunctive therapy in these patients, and more effective inhibition of platelet function is achieved than with the thienopyridine clopidogrel. Orally active antagonists are also being developed that may be more effective than the thienopyridines. Drug Dev. Res. 52:202–212, 2001. © 2001 Wiley‐Liss, Inc.
Neuroprotection during hypoxic insults: Role of adenosine
Authors: Sebastião Ana M. , de Mendonça Alexandre , Ribeiro J. Alexandre
Published: August 2002

Adenosine is released from neurones and from glial cells during hypoxic and ischaemic episodes, and, by operating membrane A1 receptors, acts as a neuroprotective agent. Evidence for this neuroprotective role of adenosine is supplied by both in vivo and in vitro studies. By evaluating the action of hypoxia on synaptic transmission in hippocampal slices, it has been shown that substances that are also released during hypoxia, such as γ‐aminobutyric acid (GABA), acetylcholine, and even glutamate may also have a neuroprotective role; however their action is evident only when activation of adenosine A1 receptors is impaired. We propose that adenosine A1 receptors have a pivotal role during hypoxia, though other substances can operate in a redundant or even overprotective manner, acting as a substitute for some adenosine actions when the nucleoside is not operative. Drug Dev. Res. 52:291–295, 2001. © 2001 Wiley‐Liss, Inc.
Modulation by adenosine A2A receptors of dopamine‐mediated motor behavior as a basis for antiparkinson’s disease drugs
Authors: Morelli Micaela , Pinna Annalisa
Published: August 2002

Several studies have evidenced the opposite role played by dopamine and adenosine receptors in the control of motor behavior. In line with those studies, we have previously shown that the acute administration of the A2A receptor antagonist SCH 58261 potentiated the turning behavior induced by L‐DOPA in the unilateral 6‐hydroxydopamine (6‐OHDA) rat model of Parkinson’s disease (PD), suggesting that selective adenosine A2A receptor antagonists might be useful as adjuncts to L‐DOPA therapy. One of the most important problems in the treatment of PD is to find a drug regimen effective after chronic administration and devoid of dyskinesia‐like side effects. Previous studies have shown that the sensitized turning response, developed in 6‐OHDA‐lesioned rats after chronic intermittent L‐DOPA, is a useful model of dyskinesia. In the present study, we evaluated the effect of a chronic administration of SCH 58261 alone or in combination with L‐DOPA in 6‐OHDA lesioned rats in order to verify the effectiveness of SCH 58261 after repeated administration and its dyskinetic potential. Repeated administration of SCH 58261 (5 mg/kg) did not produce tolerance to its ability to potentiate L‐DOPA‐turning behavior. Moreover, chronic intermittent SCH 58261 (5 mg/kg) plus L‐DOPA produced a stable turning behavior response during the course of the treatment, whereas L‐DOPA alone produced a progressive increase in turning behavior intensity and duration (sensitization). These results suggest that SCH 58261 is effective in potentiating L‐DOPA‐induced turning behavior even after a chronic treatment and it does not produce, in combination with L‐DOPA, motor response alterations. A2A receptor antagonists could be a new and useful tool for the treatment of PD. Drug Dev. Res. 52:387–393, 2001. © 2001 Wiley‐Liss, Inc.
Suppressive effects of adenosine on the 5‐lipoxygenase pathway in human polymorphonuclear leukocytes
Authors: Flamand Nicolas , Plante Hendrick , Picard Serge , Austin Michelle , Surette Marc E. , Krump Éric , Bourgoin Sylvain , Borgeat Pierre
Published: August 2002

Leukotrienes are potent mediators of inflammation and host defense. They are also involved in inflammatory and allergic diseases. While numerous studies have investigated the stimulatory mechanisms of leukotriene biosynthesis in phagocytes by inflammatory agents (chemoattractants, cytokines, etc.), the mechanisms responsible for the physiological downregulation of leukotriene biosynthesis have been the subject of very few investigations so far. It has, however, been reported that E‐type prostaglandins are potent inhibitors of leukotriene biosynthesis in chemoattractant‐stimulated neutrophils and we have recently shown with in vitro studies that endogenous adenosine is a potent inhibitor of leukotriene biosynthesis by neutrophils. The present review summarizes our studies demonstrating that adenosine downregulates leukotriene biosynthesis via an interaction with the adenosine A2a receptor on neutrophils; studies aimed at defining the mechanisms of action of adenosine in this process have demonstrated that adenosine inhibits the translocation of the cytosolic enzyme 5‐lipoxygenase to nuclear structures, a process required for leukotriene biosynthesis in neutrophils. Our studies also demonstrated that exposure of human neutrophils to the adenosine A2a receptor agonist CGS‐21680 result in a profound inhibition of the release of arachidonic acid upon cell stimulation. While the previously reported inhibitory effect of adenosine on calcium influx elicited in ligand‐activated neutrophils does not appear to be involved in the inhibitory effects of adenosine on leukotriene biosynthesis, strong evidence supports the implication of elevation of intracellular cyclic AMP concentration both in the inhibition of 5‐lipoxygenase translocation and arachidonic acid release. Drug Dev. Res. 52:397–405, 2001. © 2001 Wiley‐Liss, Inc.
Interplay of constitutively released nucleotides, nucleotide metabolism, and activity of P2Y receptors
Authors: Lazarowski Eduardo R. , Boucher Richard C. , Harden T. Kendall
Published: August 2002

At least six mammalian P2Y receptors exist that are specifically activated by ATP, UTP, ADP or UDP. Although the existence of ectoenzymes that rapidly metabolize extracellular nucleotides is well established, the relative flux of ATP and UTP through their extracellular metabolic products remains undefined. In addition, the existence of basal nucleotide release and the contribution of resting levels of ATP and UTP to P2 receptor activation are poorly understood. In the absence of exogenous agonists, an apyrase‐sensitive inositol phosphate accumulation was observed in resting 16HBE14o– human bronchial epithelial cells endogenously expressing P2Y receptors and in 1321N1 human astrocytoma cells expressing a recombinant P2Y2 receptor. To test whether nucleotide release may account for basal P2 receptor activities, the rates of extracellular accumulation and metabolism of endogenous ATP were examined with resting 16HBE14o–, C6 rat glioma, and 1321N1 cell cultures. Although extracellular ATP concentrations (1‐5 nM) remained unchanged for up to 12 h, [γ32P] ATP included in the medium (as a radiotracer) was completely degraded within 120 min, indicating that ATP release balanced ATP hydrolysis. The calculated basal rates of ATP release ranged from 20 to 200 fmol/min per million cells. HPLC analysis during steady state revealed that the gamma‐phosphate of ATP was reversibly transferred to species further identified as UTP and GTP, implicating ecto‐nucleoside diphosphokinase (NDPK)‐catalyzed phosphorylation of endogenous UDP and GDP. At steady state, the final 32P‐products of [γ32P]ATP metabolism were 32P‐orthophosphoric acid and a species further purified and identified as 32P‐pyrophosphate. Constitutive nucleotide release balanced by the concerted activities of ecto‐ATPase, ecto‐ATP pyrophosphatase, and ecto‐NDPK may determine the resting levels of extracellular nucleotides and therefore, the basal activity of P2 receptors. Drug Dev. Res. 53:66–71, 2001. © 2001 Wiley‐Liss, Inc.
Characteristics of binding sites for ATP4‐ at the human P2X7 receptor
Authors: Klapperstück Manuela , Schmalzing Günther , Markwardt Fritz
Published: August 2002

The effect of the agonist ATP4‐ on whole‐cell currents of Xenopus oocytes expressing the human P2X7 receptor (hP2X7) or a mutant with an incorporated his‐tag and additionally a truncated C‐terminus (his‐hP2X7ΔC) were investigated by means of the two‐microelectrode voltage‐clamp technique. The activation time course of hP2X7 was characterized by an exponential current growth together with a nearly linearly activating current component. HP2X7‐dependent currents deactivated biexponentially with time constants of about 1 and 5 sec after activation by ATP4‐. The amplitude of the exponentially activating current component displays a biphasic dependence on the agonist concentration, which can be best approximated by two Hill functions with Hill coefficients of 2 and dissociation constants of about 4 and 220 μM free ATP4‐ corresponding to two low‐ and two high‐affinity binding sites. The other current components are monophasically dependent on agonist concentration. The linearly activating and the slowly deactivating current components are dependent on the low‐affinity binding sites, whereas for the slowly deactivating current only the high‐affinity binding site is relevant. The effect of the low‐affinity binding sites is abolished in the his‐hP2X7ΔC mutant. It is concluded that hP2X7 receptors possess two types of binding sites with different affinities for ATP4‐ and that the distinct occupation of these sites may lead to different types of activation of the receptor. Drug Dev. Res. 53:77–82, 2001. © 2001 Wiley‐Liss, Inc.
Novel effects of a sleep‐inducing lipid, oleamide, on Ca2+ signaling in renal tubular cells
Authors: Chen Wei‐Chung , Lin Muh‐Chiou , Chou Kang‐Ju , Fang Hua‐Chang , Liu Chun‐Peng , Cheng Jin‐Shiung , Lo Yuk‐Keung , Lee Kim‐Chung , Wang Jue‐Long , Su Warren , Law Yee‐Ping , Jan Chung‐Ren
Published: August 2002

The effect of oleamide, a sleep‐inducing endogenous lipid in animal models, on intracellular free levels of Ca2+ ([Ca2+]i) in Madin‐Darby renal tubular cells was examined using fura‐2 as a fluorescent dye. Oleamide (5–50 μM) increased [Ca2+]i in a concentration‐dependent fashion with an EC50 value of 20 μM. The [Ca2+]i signal comprised an initial rise and an elevated phase and was reduced by removing extracellular Ca2+ by 50%. After pretreatment with 5–50 μM oleamide in Ca2+‐free medium, addition of 3 mM Ca2+ increased [Ca2+]i in a manner dependent on the concentration of oleamide. In Ca2+‐free medium, pretreatment with thapsigargin (1 μM), an endoplasmic reticulum Ca2+ pump inhibitor, abolished [Ca2+]i increases induced by 20 μM oleamide; conversely, pretreatment with 20 μM oleamide reduced 1 μM thapsigargin‐induced [Ca2+]i increases by 50%. Suppression of the activity of phospholipase C with 2 μM U73122 abolished 20 μM oleamide‐induced Ca2+ release. Collectively, these data demonstrate that oleamide induced significant [Ca2+]i increases in renal tubular cells by a phospholipase C‐dependent release of Ca2+ from thapsigargin‐sensitive stores and by inducing Ca2+ entry via store‐operated Ca2+ entry. Drug Dev. Res. 54:40–44, 2001. © 2001 Wiley‐Liss, Inc.
Long‐term retention of spatial navigation by preweanling rats
Authors: Carman Heidi M. , Booze Rosemarie M. , Mactutus Charles F.
Published: August 2002

The present study was designed to examine retention of spatial information in the immature, Fischer‐344N rat using a savings paradigm. Following training to locate a hidden platform using extramaze cues, preweanling animals (17 days of age) were immediately probed by testing in the tank with the platform removed. One week later, pups (26 days of age) were given an additional four training trials immediately followed by a second probe test to examine the animals' memory for the location of the platform. Animals that received initial training at 17 days of age demonstrated significant savings of information when tested after the retention interval. These data replicate our recent report of spatial navigation capabilities in the preweanling rat, and extend those findings by demonstrating that preweanling spatial navigation performance permits more rapid and accurate navigation following a 7‐day retention interval after a “reinstatement” insufficient to produce accurate navigation in maturation controls. © 2002 John Wiley & Sons, Inc. Dev Psychobiol 40: 68–77, 2002
Visual‐preference and operant measures of infant memory
Authors: Wilk Amy E. , Klein Laurie , Rovee‐Collier Carolyn
Published: August 2002

In three experiments with sixty 3‐ and 6‐month‐olds, we examined whether operant and visual‐preference measures of retention are equivalent. Infants learned to move a mobile by kicking and then received a paired‐comparison test with the familiar (training) mobile and a novel one. Kicking above baseline was the direct measure of retention, and longer looking at the novel mobile was the visual‐preference or inferred measure. Retention was tested 1 day after training (Experiment 1) or reactivation (Experiment 2) and immediately or 4 days after training (Experiment 3). Despite differences in age and retention interval, infants consistently exhibited retention on the operant measure, but not on the visual‐preference measure. These data reveal that the two measures of retention are not equivalent. When expectations are associated with a particular stimulus, infants indicate retention directly and robustly, rarely looking longer at a novel test stimulus. This result is not limited to operant situations. © 2001 John Wiley & Sons, Inc. Dev Psychobiol 39: 301–312, 2001
A study on direction‐of‐arrival estimation methods using cosθ amplitude response antenna
Authors: Inaba Takayuki , Takada Jun‐ichi , Araki Kiyomichi , Sakamoto Teijiro , Yanagisawa Hajime
Published: August 2002

At present, when the direction of arrival of a low‐frequency electromagnetic wave such as one in the HF band is measured, loop antennas are used. However, in low‐frequency measurement such as is used in underwater communications, subsurface resource detection, volcanic activity observation, and natural electromagnetic wave observation, the receiving power sensitivity decreases as the frequency is decreased. The purpose of this paper is to use a SQUID (Superconducting QUantum Interference Device), known as an ultrasensitive magnetic sensor, for construction of a small magnetic antenna for estimating the direction of arrival of low‐frequency electromagnetic waves. As a first step, the antenna configuration and direction of arrival estimation method shown below are proposed.

As a low‐frequency broadband antenna with an amplitude response type, we consider a SQUID array, which has a cosθ mode vector consisting of SQUID elements on a circle with a small radius, which is negligible in comparison with the wavelength of the incident wave.

For an antenna with a real‐valued cosθ mode vector, we consider a direction‐of‐arrival estimation method within the framework of the estimation principle of ESPRIT and MUSIC, known as high‐resolution direction‐of‐arrival estimation methods, and derive an estimation method. The obtained estimation method is shown to be ultimately reducible to a simple estimation equation for deriving the phase difference between the −1st and 1st fundamental waves after beam subspace transformation of the correlation function without eigenfunction expansion.

By computer simulation, it is shown that an estimation accuracy of 0.2 to 2° is obtained by this estimation equation for the finitely many elements and snapshots that are actually anticipated. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 85(10): 8–22, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10009
Evaluation of the normalized impedance of a transverse slot in the image plane of an image NRD guide
Authors: Chirwa Lawrence C. , Morimoto Kenji , Sugawara Yasutaka , Yamamoto Manabu , Omiya Manabu , Itoh Kiyohiko
Published: August 2002

A transverse slot placed in the image plane of the image NRD guide that has a low loss nature similar to that of the NRD guide in a millimeter wave circuit can be designed using waveguide array theory. In this paper, a method is presented to derive the normalized impedance of the transverse slot needed for the design from standing wave measurement. Near the slot, the standing wave distribution is disturbed by the field scattered from the slot. A method is given to derive the minimum distance for which no effect of the scattered field is received. From the standing wave distribution in the range where this condition is satisfied, the normalized impedance is evaluated. Further, in order to determine the validity and effectiveness of the evaluation method, an analysis based on the finite difference time domain (FDTD) method is carried out and the results are compared with the experimental data. Finally, a design example of an array antenna is presented. A possibility for applications of the proposed measurement method and the derived normalized impedance to the array antenna design is confirmed. © 2002 Scripta Technica, Electron Comm Jpn Pt 1, 85(5): 25–33, 2002
An adaptive array antenna with SLC‐type preprocessor
Authors: Hirata Kazufumi , Sekiguchi Takashi , Fujisaka Takahiko
Published: August 2002

Recently, with rapid proliferation of mobile communication, there has arisen a need for adaptive array antennas that can automatically control the antenna radiation pattern. In adaptive array antennas based on the MMSE (Minimization of Mean Square Error) method, a reference signal with a high correlation with the desired wave is required in order to distinguish the desired wave and the interference waves. The unique word (UW) employed for synchronization in mobile communication is a known signal sequence and can be used as a reference signal. However, it is necessary to accurately estimate the timing at which the UW is contained in the communication signal. The estimation error in the case of strong interference can be a cause of deterioration of the interference suppression capability. Also, if the UW is contained in both the interference and the desired wave at the same timing, the desired wave cannot be recognized and the interference wave cannot be suppressed. In this paper, an adaptive array antenna with a two‐stage configuration using a preprocessing of an SLC (sidelobe canceler) is proposed so that the effect of the interference prior to the start of communication is avoided. By the simulation, it is confirmed that only the interference wave can be suppressed effectively even if the UWs contained in the interference and the desired wave are in synchronization. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 85(7): 1–11, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1106
An interworking architecture of IN and user CT systems and services
Authors: Yamada Hideaki , Utunomiya Eiji , Masaki Hiroto , Horiuchi Hiroki , Oda Tosikane
Published: August 2002

With progress in intranet/Internet environments and computer telephony (CT) technology, it is expected that intelligent services using IP network will soon be developed. In such services, high‐grade information processing facilities, including terminals, will be actively used, making possible high performance of the user interface and highly sophisticated user‐side processing. This paper proposes a new architecture in which an interworking unit (IW‐Unit) is used in both the user‐side CT system and the net‐side IN system, with examples of added‐value services. The proposed method is a practical high‐grade service for users having CT systems. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 85(11): 106–114, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1143
Multilayer interconnect technology for scaling
Authors: Kikkawa Takamaro
Published: August 2002

With the miniaturization of silicon ultralarge‐scale integrated circuits (ULSI), the increase in interconnect delay exceeds the delay time of the transistors, and the interconnect begins to control the performance of the entire ULSI chip. To enhance further the speed of ULSI, it is necessary to solve the problem of large‐distance propagation of high‐speed signals in the large‐scale chip. The damascene multilayer interconnect integration technology is an important interconnect technology for achieving large‐scale integration and high speed in ULSI at low cost. CMP technology, Cu electroplating technology, and low‐dielectric‐constant insulating film layers are described as element process technologies required for its implementation. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 84(4): 26–40, 2001
Influence of electrical source impedance on phase shift of sound wave in the ultrasonic velocity measurement
Authors: Sasaki Daizo , Imano Kazuhiko , Inoue Hiroshi
Published: August 2002

In acoustic velocity measurement using ultrasonic waves, the composite resonator method with the sample and the transducer becomes a source of error. This phenomenon is considered as a phase shift at the boundary between the transducer and the sample and is analyzed by numerical simulation. From the result, it is found that the phase shift depends on the electrical source impedance and that the phase shift can be minimized by setting the electrical source impedance equal to the reactance of the transducer at resonance, depending on the acoustic condition of the backing of the transducer. The results of experiments with a varying electrical source impedance are found to be similar to those of simulations. Further, it becomes possible to measure the acoustic velocity of water with a discrepancy of less than 0.1% from the referenced value if the phase shift is eliminated by taking the propagation time difference in two samples with different lengths. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 84(4): 41–48, 2001
Detection performance of coherent signals by the polarization averaging MUSIC algorithm
Authors: Yamada Hiroyoshi , Yamakura Toshiharu , Yamaguchi Yoshio
Published: August 2002

In remote sensing and the evaluation of radio wave propagation, there has recently been interest in highly accurate estimation methods with high resolution, including polarization information. In the superresolution method, which realizes a high resolution that cannot be achieved by the Fourier transform method, several reports have been presented on the use of polarization information. This paper considers polarization‐averaging correlation reduction preprocessing, which is one of the methods of utilizing polarization data in the superresolution method. The correlation reduction performance when combined with SSP and MSSP is examined from theoretical and quantitative standpoints. It is shown by computer simulation that the MSSP method combined with polarization averaging can effectively reduce correlation by utilizing polarization, and that it achieves a higher estimation accuracy than other methods in propagation estimation with a smaller number of snapshots. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 84(7): 1–9, 2001
The effect of surface oxidation status on 0.35‐μm HIGFET characteristics
Authors: Ohshika Katsushi , Kuroda Jun , Yanazawa Hiroshi
Published: August 2002

The paper discusses the effect of the oxide film formed on the surface of GaAs substrate of the gate metal of 0.35‐μm WSi gate HIGFET (Heterostructure Insulated Gate FET) on its characteristics. An optimized SiON film (refractive index 1.58) deposited by plasma CVD method onto the entire HIGFET surface was used as a passivation film to protect the gate metal substrate [1]. In order to modify oxidation conditions on the GaAs surface, two oxidation methods were utilized: low‐temperature oxidation (further referred to as UV/O3 oxidation), which utilizes O3 generated from the atmospheric O2 by applying ultraviolet irradiation produced by a mercury lamp (184.9 and 253.7 nm), and high‐temperature thermal oxidation performed at 400 °C in air. Based on the results of spectroscopic ellipsometry, Auger spectrometry, and XPS analyses, it was the UV/O3 method that led to formation of thermally unstable SiON/GaAs oxide film on the GaAs interface layer due to higher concentration of As oxide. During the heat treatment, involved in the FET fabrication process, As oxide would react with SiON resulting in its thermal decomposition and formation of free As. On the other hand, the oxide film formed during thermal oxidation at 400 °C led to formation of more thermally stable SiON/GaAs oxide film/GaAs interface layer due to higher concentration of Ga oxide via decomposition of thermally unstable As oxide during the heating process. In either case, the presence of GaAs oxide film along with free As in the SiON passivation film deposited onto GaAs substrate is believed to be a major reason for declining FET characteristics. This suggests that removal of the oxide film from the surface prior to depositing a passivation film is required. The improved stability of the FET characteristics was achieved by removing the GaAs oxide film using wet etching with BHF during the FET fabrication process. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 84(7): 46–57, 2001
A new transition from rectangular waveguide to image NRD guide
Authors: Hattori Kazuya , Yamamoto Manabu , Itoh Kiyohiko
Published: August 2002

The image NRD guide as a modification of the NRD guide is expected to find applications at millimeter wave frequencies. In order to construct circuits and antennas containing image NRD guides and to evaluate their characteristics, a transition to another waveguide is needed. In this paper, a transition structure from a rectangular waveguide to an image NRD is proposed and its operating principle is explained. Also, by means of numerical calculations based on the effective dielectric constant (EDC) method, a transition intended for use in the R band (30 GHz) is designed. Further, the designed transition is measured and the effectiveness of the proposed transition is demonstrated. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 84(10): 9–16, 2001
Electromagnetic wave simulation of honeycomb sandwich structures by 3D volume integral equations
Authors: Takahashi Yasuo , Suzuki Shinobu , Matsuda Syuji , Tanaka Kazuo , Tanaka Masahiro
Published: August 2002

The shape of the honeycomb core must be considered in the analysis of the problem of electromagnetic wave scattering in a honeycomb sandwich structure at high frequency. The three‐layer sandwich structure has the characteristic of having a very small dielectric region with respect to its entire volume, since it has a structure in which the upper and lower skin sandwich between them a honeycomb core which contains many honeycomb‐shaped holes. On the other hand, volume integral equations have the advantage of discretizing only the dielectric region, since only the polarized electric current of the dielectric region is an unknown. Thus, electromagnetic wave simulation of the three‐layer honeycomb sandwich structure by using volume integral equations is considered to be an effective means for large‐scale precision analyses. This paper reports a numerical computing method that takes account of the shape of the honeycomb core, applying three‐dimensional volume integral equations to the electromagnetic wave scattering problem of the three‐layer honeycomb sandwich structure, and the results of code verification by means of the optical theorem and its reciprocity are presented. In addition, the effectiveness of the proposed numerical computing method is shown by identifying the effects of the honeycomb core on the electrical field intensity distribution inside the skin. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 84(10): 24–33, 2001
A theoretical study on suppression of scattering by a perfectly conductive cylinder array
Authors: Aoyagi Takahiro , Nishikata Atsuhiro , Hashimoto Yasuo , Ishino Ken , Shimizu Yasutaka
Published: August 2002

In this paper, TV ghosts produced by the metal suspension cables of a large suspension bridge are studied. Improvement of the D/U ratio at the receiving point is investigated. It is demonstrated by calculations and experiments that by loading the metal cylinders with a cylindrical ferrite, the relative scattering intensity in the 0 to 90° range in the horizontal plane can be reduced. By loading cylindrical dielectric materials the relative scattering intensity can be reduced by about 8 dB, while scattering in other directions increases. Hence, by using a cylindrical absorber made of a combination of a dielectric material and rubber ferrite, suppression of the scattering at more than 90° on one side is investigated. Theoretical calculations of the scattering properties are carried out by means of the multiple multipole program (MMP) method. It is shown that the relative scattering intensity near 120° can be reduced to less than –10 dB without increase of scattering in other directions. It is therefore shown theoretically that the D/U ratio can be improved. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 84(11): 41–50, 2001
Terahertz‐wave parametric generation characteristics of MgO:LiNbO3
Authors: Ken‐ichi Karino , Jun‐ichi Shikata , Kodo Kawase , Hiromasa Ito , Ietaka Sahashi
Published: August 2002

This paper describes the terahertz‐wave generation characteristics and mechanism of a terahertz‐wave parametric oscillator (TPO) using MgO:LiNbO3, which has high optical damage resistance. We have observed that congruent MgO:LiNbO3 shows fivefold higher THz‐wave output characteristics compared to undoped LiNbO3. To find the optimum concentration of MgO and to study the mechanism of output increase, we measured the THz‐wave parametric generation (TPG) and far‐infrared spectral characteristics of MgO:LiNbO3 samples having different doping concentration. We found that the optimum concentration is 5 mol% and that output is increased due to an increase in parametric gain resulting from the increased Raman scattering cross section and increased lifetime of the lowest A1‐symmetry phonon mode. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 85(4): 22–29, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.1101
Vehicular speed response adaptive antenna
Authors: Hamamura Masanori , Tachikawa Shin'ichi
Published: August 2002

When an adaptive antenna is used on the downlink receiver side of a moving vehicle, especially in the presence of high‐speed fading, the received signal becomes unsteady and the communications performance is significantly degraded because the updating of the antenna weight is not carried out accurately. In order to resolve this problem, this paper proposes a vehicular speed response adaptive antenna (VSR‐AA). Its performance in a Nakagami–Rice fading environment is evaluated by computer simulation. In order to operate the vehicular speed response VCO, which plays an important role in the proposed VSR‐AA, the angle of arrival of the direct wave must be known. It is shown that the direction can easily be estimated with sufficient accuracy from the maximum gain direction of the characteristic of the adaptively formed beam. By using the proposed VSR‐AA, an improvement of about 10 dB in Eb/N0 at BER = 10−2 can be obtained over the conventional adaptive antenna under the conditions of a Rice factor of 5.0, eight antenna elements, and fDT (product of the maximum Doppler frequency and data symbol length) = 0.05. Further, the BER is substantially degraded in the conventional system as fDT becomes larger. On the other hand, in the proposed system, the BER obtained is almost constant so that a high degree of communications quality is maintained. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 85(8): 11–21, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.10004
Design of IIR digital filters with flat passband and equiripple stopband responses
Authors: Zhang Xi , Yoshikawa Toshinori
Published: August 2002

In the design of IIR digital filters, the method that utilizes the classic analog filter design theory to design analog filters and then obtain the corresponding digital filters by s–z transformation is well‐known. However, IIR digital filters obtained via the bilinear s–z transformation have just equal‐order numerator and denominator. Having unequal‐order numerator and denominator will give more degrees of freedom in filter design. In this paper, we consider the design of IIR digital filters with unequal‐order numerator and denominator, and propose a method for designing the flat passband and equiripple stopband filters in z‐domain directly. First, we present a design method of IIR filters with flat stopband and equiripple passband responses. The flat stopband response can be easily obtained only by locating multiple zeros on the specified frequency points, while the equiripple passband response can be designed by using the Remez exchange algorithm and specifying the maximum magnitude error. Second, we can obtain IIR filters with flat passband and equiripple stopband responses via a magnitude transformation such that the passband and stopband become the corresponding stopband and passband, respectively. However, the numerator order of IIR filters obtained by the above method is equal to or higher than the denominator. Finally, we consider the design of IIR filters that have lower‐order numerator than denominator, and present a method for designing the flat passband and equiripple stopband filters directly. © 2001 Scripta Technica, Electron Comm Jpn Pt 3, 84(11): 37–44, 2001
A simple quantum computer: Experimental realization of quantum computation algorithms with linear optics
Authors: Takeuchi Shigeki
Published: August 2002

In efforts toward the realization of quantum computers, there have been many proposals to implement controlled NOT gates between quantum bits (qubits). However, the number of quanta in the experimentally realized system has been at most two. Because it is difficult to cope with both the realization of the conditional interaction (e.g., huge nonlinear interaction) between the quanta, and the maintenance of quantum coherence for a sufficient time, the realization of quantum logic gates using several quanta may be difficult in the near future. In this paper, a new method which implements a quantum algorithm using linear optics and single photons is described. This method does not need any huge nonlinearity. Hence, it is practical with today's technology and will be one of the useful physical test beds for the quantum algorithms. The optical implementation of the Deutsch–Jozsa algorithm with a 4‐bit input is proposed, and the mechanism is explained. As one instance of the recent progress of our project, an experiment of single‐photon interference using parametric fluorescence with highly stabilized interferometer system is reported. © 2001 Scripta Technica, Electron Comm Jpn Pt 3, 84(11): 52–60, 2001
Chaos communication using unknown input observers
Authors: Inoue Eiji , Ushio Toshimitsu
Published: August 2002

Chaos synchronization is a phenomenon in which two chaotic subsystems have equal states at each time step. In this paper, a design method is briefly described for unknown input observers used in system theory. Next, a chaos communication method based on design technique that achieves restoration of the information signals by chaos synchronization between a transmitter and a receiver is proposed. Further, with a view to improving the performance of resisting noise, an improved method is proposed by introducing the least‐squares method. The performance of the proposed communication method is tested by simulation. © 2001 Scripta Technica, Electron Comm Jpn Pt 3, 84(12): 21–27, 2001
A Fourier coefficient estimation method based on notch filters and an adaptive algorithm for sinusoidal signals in additive noise
Authors: Kudoh Norimasa , Tadokoro Yoshiaki
Published: August 2002

Estimating the amplitude and phase of a signal accurately even when the frequencies contained in the signal are already known is very important in many areas. The estimation accuracy and the estimation time are important issues in such areas and a method of improving both of these issues by combining the notch characteristics and the band passing characteristics of serially connected notch filters and an adaptive algorithm is presented in this paper. Computer simulations reveal that the performance of the proposed method is superior to previously proposed methods. © 2001 Scripta Technica, Electron Comm Jpn Pt 3, 85(2): 65–73, 2002
Optimal design of diagnosable systems on networks constructed by graph operations
Authors: Araki Toru , Shibata Yukio
Published: August 2002

In this paper, we consider self‐diagnosable systems on computer networks, known as one‐step t‐fault diagnosable systems introduced by Preparata and colleagues. In order to give network topologies, some graph operations such as the Cartesian product, the Kronecker product, and the line digraph operation are utilized. We study the diagnosability of networks constructed by the graph operations based on the idea of “highly structured system,” and then present some optimal networks. © 2002 Scripta Technica, Electron Comm Jpn Pt 3, 85(5): 1–9, 2002