bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiple‐tuned liquid column dampers for torsional vibration control of structures: theoretical investigation
Authors: Xu Y. L. , Shum K. M.
Published: December 2002

This paper presents a theoretical investigation on the performance of multiple‐tuned liquid column dampers (MTLCD) for reducing torsional vibration of structures in comparison with single‐tuned liquid column dampers (STLCD). The analytical model is first developed for torsional vibration of a structure with an MTLCD under either harmonic excitation or white noise excitation. The experimental results are then used to verify the analytical model for coupled MTLCD‐structure systems under harmonic excitation. The performance of an MTLCD and its beneficial parameters for achieving the maximum torsional response reduction to white noise excitation are finally investigated through an extensive parametric study in terms of the distance from the centre line of the MTLCD to the rotational axis of the structure, the ratio of the horizontal length to the total length of liquid column, frequency bandwidth, head‐loss coefficient, the number of TLCD units in an MTLCD, frequency‐turning ratio and the spectral level of excitation moment. The results show that there is an optimal head‐loss coefficient and an optimal frequency bandwidth for an MTLCD to achieve the maximum torsional response reduction. It is also demonstrated that the sensitivity of an optimized MTLCD to the frequency‐tuning ratio is less than that of an optimized STLCD, and it can be further improved by increasing the bandwidth but at the cost of less torsional vibration reduction. Copyright © 2002 John Wiley & Sons, Ltd.
O6‐methylguanine‐DNA methyltranspherase gene expression in gliomas by means of real‐time quantitative RT‐PCR and clinical response to nitrosoureas
Authors: Tanaka Satoshi , Kobayashi Ikuo , Utsuki Satoshi , Oka Hidehiro , Fujii Kiyotaka , Watanabe Takashi , Nagashima Tadashi , Hori Tomokatsu
Published: December 2002

O6‐methylguanine‐DNA methyltransferase (MGMT) mRNA expressions were examined in 100 neuroepithelial tumors by real‐time quantitative reverse transcription‐polymerase chain reaction (RT‐PCR) using SYBR Green I. The mean relative quantitation value of MGMTmRNA normalized to the level of β2‐microglobulin for 100 tumors was 5.3 ± 11.2. The mean value of 41 glioblastomas was significantly higher than that for the other 59 tumors (p = 0.0008 by Student's t‐test). In contrast, the means of 19 low‐grade gliomas and 12 medulloblastomas were significantly lower than that of other tumors (p = 0.0282 and p = 0.0456 by Student's t‐test). Among the 55 retrospective patients who had been treated with 1‐(4‐amino‐2‐methyl‐5‐pyrimidynyl)methyl‐3‐(2‐chloroethyl)‐ 3‐nitrosourea hydrochloride (ACNU), the value was a significant independent predictor of the effect of initial therapy with ACNU (p = 0.0007 by Mann‐Whitney U‐test) and the survival period (p = 0.0175 by Wald test). The value ≧1 was the most significant factor in predicting the initial effect of treatment by multi‐variant regression analysis (p < 0.0001). These results suggest that our individual adjuvant therapy based on MGMTmRNA expression may be improved by the application of real‐time quantitative RT‐PCR. © 2002 Wiley‐Liss, Inc.
Role of XIAP in the malignant phenotype of transitional cell cancer (TCC) and therapeutic activity of XIAP antisense oligonucleotides against multidrug‐resistant TCC in vitro
Authors: Bilim Vladimir , Kasahara Takashi , Hara Noboru , Takahashi Kota , Tomita Yoshihiko
Published: December 2002

XIAP directly inhibits executor caspases, making it the most downstream antiapoptotic molecule. Here, we examined the expression and function of XIAP in normal urothelium and TCC. We also examined the therapeutic effect of xiap AS PODN on the cell cycle and apoptosis of multidrug‐resistant T24 bladder cancer cells. XIAP was moderately expressed in normal transitional epithelium with prominent expression on the superficial layer cells. Seventy‐nine of 108 (73.15%) tumor samples were positive for XIAP protein, but XIAP positivity was not correlated with tumor stage or grade. Moreover, 4 bladder cancer cell lines (SCaBER, HT1376, T24 and RT4) expressed similar levels of XIAP. xiap AS PODN dose‐dependently reduced the XIAP protein level and induced apoptosis, leading to decreased cell viability by 87%. Combined administration with doxorubicin resulted in marked cytotoxicity due to escalation of apoptosis. Overexpression of XIAP in T24 cells resulted in a modest but statistically significant (p < 0.01) survival advantage compared to parental cells. Thus, XIAP expression may be critical for maintaining the viability and drug resistance of TCC, and endogenous XIAP levels are sufficient to protect cells from apoptosis. Our results suggest that XIAP may play an important role early in human TCC carcinogenesis. xiap AS may be a candidate for use as a cancer therapy for overcoming drug resistance in highly malignant TCC. © 2002 Wiley‐Liss, Inc.
The prognostic impact of cytokeratin‐positive cells in bone marrow of patients with localized prostate cancer
Authors: Lilleby Wolfgang , Nesland Jahn M. , Fosså Sophie D. , Torlakovic Goran , Waehre Håkon , Kvalheim Gunnar
Published: December 2002

Our study evaluates the prognostic significance of the cytokeratin‐positive mononuclear cells (CK+ cells) in the bone marrow (BM) and peripheral blood (PB) as detected by immunocytochemistry in patients with locoregionally confined prostate cancer. BM and PB samples were obtained from 66 newly diagnosed patients with T1‐4pN0M0 prostate cancer. All samples were analyzed by standardized immunocytochemical methods (anticytokeratin mononuclear antibody; AE1/AE3) applying a negative immunomagnetic cell enrichment technique. A second sampling was obtained in 60 of the 66 patients ≥2 years after definitive radiotherapy. The median follow‐up after high‐dose radiotherapy of the patients was 65 months. For the analysis of the postradiotherapy clinical progression‐free survival (PFS) treatment, failure was defined as pelvic tumor growth or development of distant metastases. At diagnosis CK+ cells were found in BM in 14 of 66 (21%) prostate cancer patients. This was not associated with an increased risk of progression. On the other hand, the presence of CK+ cells in 12 of 60 (20%) patients at the second BM aspiration was significantly related to a shorterPFS (p = 0.02). In the multivariate analysis, the presence of CK+ cells in the posttreatment BM did not remain as an independent variable of PFS assessment if posttreatment PSA was entered into the analysis. CK+ cells in PB were found in 12% of the patients. After therapy, none of the patients had detectable CK+ cells in PB. The presence of CK+ cells in the posttreatment but not in the pretreatment BM was associated with decreased PFS in patients irradiated for pelvis‐confined nonmetastatic prostate cancer. Although this association was not retained in multivariate analysis, our observations indicate that the presence of CK+ cells after local therapy define a group of patients that have a high risk of developing distant metastases. © 2002 Wiley‐Liss, Inc.
Cognate interactions between memory T cells and tumor antigen‐presenting dendritic cells from bone marrow of breast cancer patients: Bidirectional cell stimulation, survival and antitumor activity in vivo
Authors: Bai Lianhua , Beckhove Philipp , Feuerer Markus , Umansky Viktor , Choi Carmen , Solomayer Florian Schütz Erich‐Franz , Diel Ingo J. , Schirrmacher Volker
Published: December 2002

Dendritic cells (DC) and T cells were generated from Ficoll separated bone marrow (BM) mononuclear cells of primary operated breast cancer patients according to new cell culture protocols. BM‐DC were capable of functioning as professional antigen‐presenting cells (APCs) and of inducing autologous antigen‐specific memory T‐cell responses to either tetanus toxoid recall antigen or to breast cancer antigens. Treatment with lipopolysaccharide (LPS) resulted in phenotypic and functional maturation of BM‐DC. When BM‐DC, pulsed with breast cancer‐associated tumor antigens, were cocultured with autologous patient‐derived BM‐T cells to allow for cognate breast cancer antigen recognition and stimulation, apoptosis of T cells—which occurred in noncognate coculture systems—was inhibited. Furthermore, in cocultures allowing for antigen‐specific cognate interactions, the expression on BM‐DC of CD83, MHC class II, CD40 and CD86 molecules was upregulated and the cytokines IL‐12 and IFN‐α were produced in significantly elevated amounts. Adoptive transfer of breast cancer‐reactive memory T cells together with APCs into human breast cancer‐bearing NOD/SCID mice caused a regression of the tumor and prolonged survival of the animals. This was not the case when such animals had been treated by transfer of reactivated BM T cells without BM‐DCs. Our findings suggest that cognate interactions between cancer patient‐derived memory BM‐T cells and tumor antigen‐presenting BM‐DCs are important for reciprocal cell stimulation, survival and therapeutic activity. © 2002 Wiley‐Liss, Inc.
An association of Bcl‐2 phosphorylation and Bax localization with their functions after hyperthermia and paclitaxel treatment
Authors: Salah‐eldin Alaa‐eldin , Inoue Shoichi , Tsukamoto Shigeki , Aoi Hiromi , Tsuda Masumi
Published: December 2002

Apoptosis is induced by many kinds of therapy‐related inducers, such as hyperthermia and chemotherapeutic agents. However, differences in apoptotic pathways between these inducers remain unclear, although knowing the differences is important to map out a therapeutic strategy. Therefore, we focused on the localization and phosphorylation of Bcl‐2 and Bax, key mediators of the apoptotic pathway, after hyperthermia and paclitaxel treatment of PC‐10 squamous cell carcinoma cells that excessively expressed Bcl‐2 and Bax in the cytoplasm. Paclitaxel treatment markedly induced qualitative changes in Bcl‐2, whereas hyperthermia did only quantitative changes in Bax. The levels of Bax increased gradually with the duration of hyperthermia, whereas Bcl‐2 levels slightly decreased. On the other hand, paclitaxel treatment induced dose‐ and time‐dependent phosphorylation of Bcl‐2. Interestingly, phosphorylated Bcl‐2 was observed in the specific subcellular sites, mitochondria‐ and lysosome‐rich fractions. Both treatments disturbed the heterodimerization of Bax with Bcl‐2. Hyperthermia, but not paclitaxel treatment, induced a gradual Bax translocation from the cytoplasm to the nucleus. Although both treatments induced a prominent cell cycle disturbance in the G2M phase, paclitaxel treatment induced typical apoptosis, and hyperthermia hardly induced apoptosis. Our results suggest that the subcellular redistribution of Bax and the phosphorylation of Bcl‐2 depend on the type of apoptosis inducers, such as hyperthermia and paclitaxel, and Bcl‐2 has a central role in the decision of apoptotic outcome. Our data may afford new insights in apoptosis from the aspect of an association of Bcl‐2 phosphorylation with intracellular Bax localization. © 2002 Wiley‐Liss, Inc.
Polycyclic aromatic hydrocarbon‐inducible DNA adducts: Evidence by 32P‐postlabeling and use of knockout mice for Ah receptor‐independent mechanisms of metabolic activation in vivo
Authors: Kondraganti Sudha R. , Fernandez‐Salguero Pedro , Gonzalez Frank J. , Ramos Kenneth S. , Jiang Weiwu , Moorthy Bhagavatula
Published: December 2002

There is significant human exposure to polycyclic aromatic hydrocarbons (PAHs), many of which are potent carcinogens in laboratory animals and are suspected human carcinogens. The PAHs are bioactivated by cytochrome P450 (CYP)1A1/1B1 enzymes to reactive intermediates that bind to DNA, a critical step in the initiation of carcinogenesis. The Ah receptor (AHR) plays a critical role in the induction of CYP1 enzymes (i.e., CYP1A1, 1A2 and 1B1) by PAHs such as benzo[a]pyrene (BP) and 3‐methylcholanthrene (MC). In our investigation, we tested the hypothesis that AHR‐null animals are less susceptible to PAH‐induced DNA adduct formation than wild‐type animals. Wild‐type [AHR (+/+)] mice or mice lacking the gene for the AHR were treated with a single dose (100 μmol/kg) of BP or MC, and hepatic DNA adducts were analyzed by 32P‐postlabeling. BP induced multiple hepatic DNA adducts in wild‐type as well as AHR‐null animals, suggesting the existence of AHR‐independent mechanisms for BP metabolic activation. On the other hand, DNA adduct formation was markedly suppressed in AHR‐null animals exposed to MC, although the major MC‐DNA adduct was produced in these animals. Hepatic activities and apoprotein contents of 7‐ethoxyresorufin O‐deethylase (EROD) (CYP1A1) and 7‐methoxyresorufin O‐demethylase (MROD) (CYP1A2) activities were markedly induced by BP and MC in the wild‐type, but not, in AHR‐null animals. CYP1B1 expression was also induced, albeit to a lesser extent by the PAH MC, but not BP, in the wild‐type animals. In conclusion, these results demonstrate the existence of AHR‐ and CYP1A1‐independent mechanisms of PAH metabolic activation in mouse liver, a phenomenon that may have important implications for PAH‐mediated carcinogenesis. © 2002 Wiley‐Liss, Inc.
Vitamin and carotenoid intake and risk of squamous cell carcinoma of the skin
Authors: Fung Teresa T. , Spiegelman Donna , Egan Kathleen M. , Giovannucci Edward , Hunter David J. , Willett Walter C.
Published: December 2002

Our objective was to examine prospectively the intake of vitamins A (including retinol and total vitamin A), C and E; folate; total carotene; and several individual carotenoids (α‐carotene, β‐carotene, β‐cryptoxanthin and lutein/zeaxanthin) in relation to incidence of SCC of the skin in 2 large cohorts of men and women. We used a prospective cohort study design with up to 14 years of follow‐up in women and 10 years in men. Diet was measured with FFQs every 2–4 years; cases of SCC of the skin were ascertained on biennial questionnaires and confirmed by medical records. Participants were female nurses and male health professionals, from the Nurses' Healthy Study and the Health Professionals Follow‐up Study in the United States, without a history of any cancer in 1982 (n = 85,944 women) and 1986 (n = 43,867 men). Follow‐up response was achieved for over 90% of potential person‐years. Relative risks and 95% confidence intervals for development of SCC of the skin are reported. We recorded 369 cases of SCC in women and 305 cases in men. After multivariate adjustment for various known behavioral, sun‐exposure and sun‐sensitivity risk factors for SCC, there were no significant inverse associations between these dietary factors and SCC incidence. No evidence was found that vitamins A, C and E; folate; or carotenoids play an important protective role against incident SCC. © 2002 Wiley‐Liss, Inc.
Pharmacology of protoporphyrin IX in nude mice after application of ALA and ALA esters
Authors: Moan Johan , Ma Li‐Wei , Juzeniene Asta , Iani Vladimir , Juzenas Petras , Apricena Fabio , Peng Qian
Published: December 2002

Aminolevulinic acid (ALA), ALA methylester (ALA‐Me) and ALA hexylester (ALA‐Hex) were topically applied for 5 and 20 hr, respectively, on normal skin of mice. The distribution of protoporphyrin IX (PpIX) induced in 7 different tissues by these drugs was determined either by spectrofluorometric measurements with an optical fibre probe or by chemical extraction of PpIX from the tissues. The results from these 2 types of measurements were compared. Both methods showed that ALA and the esters induced similar amounts of PpIX at the skin spot where they were applied and that the esters produced much less PpIX at remote skin spots (i.e., spots outside the location where the drugs were applied) than ALA did, notably after 20 hr application. After 20 hr of drug application ALA produced much more PpIX in liver, intestine and lungs than the esters did. In contrast with the direct fluorescence measurements, the extraction method showed detectable amounts of PpIX in liver, intestine and lung after application of the esters, notably of ALA‐Me. The discrepancy is probably related to the fact that the pigmented tissues absorb light and, therefore, the direct fluorescence readings are misleading. Notably in the liver, which contains high concentration of light‐absorbing pigments, very weak direct fluorescence was seen. In no case there was any accumulation of PpIX in muscle tissue nor in brain. The esters seem to penetrate less into the circulation than ALA, and PpIX formed by them in the skin is faster cleared than PpIX formed from ALA. This is also true after oral and i.p. administration of the drugs. © 2002 Wiley‐Liss, Inc.
SULT1A1 polymorphism and esophageal cancer in males
Authors: Wu Ming‐Tsang , Wang Yi‐Ting , Ho Chi‐Kung , Wu Deng‐Chyang , Lee Yung‐Chie , Hsu Hon‐Ki , Kao Ein‐Long , Lee Jang‐Ming
Published: December 2002

Sulfotransferase (SULT) 1A1 detoxifies and bioactivates a broad spectrum of substrates including xenobiotics. It has been suggested that the SULT1A1 his (histidine) allele, which is caused by a his for arg (arginine) substitution due to a G→A transition at codon 213, carries a significantly higher risk for women to develop breast cancer. We investigated the association between the SULT1A1 arg/his genotype and esophageal cancer in men, 187 cases of esophageal squamous cell carcinoma and 308 controls from 3 medical centers in Taiwan. Cigarette smoking, areca chewing and alcohol consumption were the major risks for developing esophageal cancer. The frequencies of arg/his in cases and controls were 27.8% (52/187) and 11.0% (34/308), respectively (p < 0.0001). No subjects carried his/his. After adjusting for substance use and other covariates, individuals with arg/his had a 3.53‐fold higher risk (95% CI = 2.12–5.87) of developing esophageal cancer than those with arg/arg. Unexpectedly, this positive association was found to be even stronger (adjusted OR = 4.04–4.80) among non‐smokers, non‐drinkers or non‐chewers. Our findings suggest that the SULT1A1 his213 allele is important in the development of esophageal cancer in men. © 2002 Wiley‐Liss, Inc.
On the field patterns of the TE modes in antipodal ridge waveguide by finite element method
Authors: Lu Mai , Leonard Paul J.
Published: December 2002

In this paper, the field patterns of the TE modes in antipodal ridge waveguide (ARW) and double antipodal ridge waveguide (DARW) are presented by finite element method. The figures in this paper are useful in the design of antipodal waveguide components for wideband microwave transmission. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 79–82, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10679
Broadband characteristics of a parallel diode linearized amplifier
Authors: Mok Ka Tsun , Chan Wing Shing , Leung Chun Kai , Yu Chi Sun , Li Chung Wai
Published: December 2002

A compact broadband linearized amplifier, using a parallel‐configured diode connected directly to the base of the transistor, is proposed. It has shown a reduction in spectral re‐growth of 8–20 dB for the first sidelobe in the frequency range of 0.8–2 GHz. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 82–83, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10680
Performance analysis of Comb filters based on sampled fiber Bragg gratings
Authors: Sun Junqiang
Published: December 2002

Reflection performances of sampled Bragg gratings are simulated using the piecewise‐uniform method. The identical characteristics of reflection spectrum are emphasized in terms of the linewidth and reflectivity. A perfect comb filter with identical channel linewidth and uniform reflectivity is demonstrated, employing the sinc‐sampled grating. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 84–87, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10681
A phase‐shifting frequency discriminator employing dielectric resonator
Authors: Yuksel Emine Yesim , Wong Thomas T. Y.
Published: December 2002

A planar circuit realization of a frequency discriminator based on single‐mode operation of the dielectric resonator is presented. Drawing on the phase‐shifting action of the dielectric resonator, the discriminator function can be achieved with one detector diode, thus adding to the simplicity of the design. It is demonstrated with measurements on the performance of discriminators implemented with dielectric resonators having different temperature coefficients that effective frequency stabilization by thermal compensation for the substrate material can be facilitated by the additional degree of freedom brought about by the dielectric resonator. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 87–89, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10682
Injection locking of an erbium‐doped fiber laser‐amplifier
Authors: Teyo T. C. , Shah N. S. M. , Ahmad H.
Published: December 2002

Injection locking of an erbium‐doped fiber laser‐amplifier is presented. Inside the locking range, the system oscillates at the wavelength of the injected signal. Outside the locking range, both signal and laser oscillate simultaneously in the cavity. Signal detuning studies show that the locking range increases with higher input signal power. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 89–91, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10683
The fractal Hilbert monopole: A two‐dimensional wire
Authors: Anguera Jaume , Puente Carles , Martínez Enrique , Rozan Edouard
Published: December 2002

A novel miniature antenna based on the fractal Hilbert geometry is presented. The antenna becomes electrically smaller as the fractal iteration increases at a higher rate than that of any other fractal geometry presented until now. Several fractal‐shaped Hilbert monopoles have been constructed, measured, and compared with the classical λ/4 monopole. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 102–104, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10687
Longitudinal coupled‐cavity scheme for microwave‐excited CO2 slab lasers
Authors: Shahadi A. , Sintov Y. , Jerby E.
Published: December 2002

A new microwave‐excited CO2 slab‐laser scheme is demonstrated in a slow gas‐flow laser experiment. The gas‐discharge axial homogeneity is improved by an H‐plane coupling of a rectangular resonator operating in the fundamental mode to a shorter slab laser‐head resonator, below the cutoff. This paper describes the conceptual experimental and practical aspects of the microwave‐excited laser. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 115–120, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10692
Analysis of a bilateral distributed amplifier using scattering parameters
Authors: Moussa Mehdi Si , Trabelsi Mohamed , Aksas Rabia
Published: December 2002

A formulation for the bilateral distributed amplifier network using a normalized transmission matrix approach is proposed in this letter. The analysis takes into consideration the effect of Cgd in the active device. Our approach is compared to the theoretical predictions for the unilateral case and measured results. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 120–122, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10693
Resonance absorption in single and cascaded lossy waveguide‐dielectric resonators
Authors: Minakova Lyudmila B. , Rud Leonid A.
Published: December 2002

An approximate theory of lossy waveguide‐dielectric resonators (WDRs) is developed. The theory is based on a search for the resonator's natural oscillations providing the required ratio between the radiation and intrinsic Q factors. This allows us to predict and control the level of absorbed power by changing the oscillation coupling or loss coefficient. The theory's limitations and validity are verified by a comparison with the exact numerical results obtained for the resonators, which are formed by rectangular dielectric posts and partially filled H‐plane stubs in a rectangular waveguide. Potential applications of the developed theory for the design of narrowband absorption filters are demonstrated. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 122–126, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10694
A tuning slot modified dual‐mode bandpass filter on Al2O3 substrate
Authors: Yang Cheng‐Fu , Tzou Wen‐Cheng , Chen Ying‐Chung , Lee Tsung‐Hsien , Cheng Ping‐Shou
Published: December 2002

One planar dual‐mode bandpass filter with circle‐type patch and square slot is simulated, fabricated, and measured using an Al2O3 substrate. The circle‐type patch and microstrip lines are fabricated through copper evaporation. The square slot is used to shift the resonant frequency, and the resonant frequency is shifted to lower frequency as slot size increases. Our measured results show that square‐slot‐modified dual‐mode bandpass filters present a number of attractive features for practical application. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 126–129, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10695
A novel method for short leaky‐wave antennas to suppress the reflected wave
Authors: Wang Chien‐Jen , Guan Hua‐Lin , Jou Christina F.
Published: December 2002

A method to suppress the back lobe of a short leaky‐wave antenna (LWA) by using an aperture‐fed patch antenna on the backside is demonstrated in this paper. The aperture‐fed patch antenna is connected to the open end of the LWA. This design offers another radiation path of the reflected wave and creates another radiation pattern on the back plane of the substrate. Experimental results show that the suppression of the reflected wave can be 10 dB at 10.0 GHz with an LWA length of 6 cm (2 wavelengths). Compared to the conventional design, this novel structure can radiate as efficiently as LWA at a length of 4 wavelengths. The two radiation patterns on different planes have great potential in many applications and can provide more flexibility to traditional designs. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 129–131, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10696
Low‐profile broadband printed quadrifilar helical antenna for broadcasting satellite application
Authors: Chen Yen‐Yu , Wong Kin‐Lu
Published: December 2002

This paper presents a low‐profile broadband design of a printed quadrifilar helical antenna for the application as a broadcasting satellite receiving antenna in the frequency range of about 2.3 to 2.7 GHz. The antenna comprises four parallel printed strips excited in phase quadrature and rolled into a helical shape on a foam cylinder of diameter 22 mm and height 27.2 mm. The antenna shows broadband circular polarization (CP) operation with a 3‐dB axial‐ratio bandwidth of about 670 MHz or 27.9% centered at about 2.4 GHz. Good antenna gain is also obtained. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 134–136, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10698
Analysis of conformal antennas on a complex platform
Authors: Liu Jian , Jin Jian‐Ming
Published: December 2002

A numerical technique is presented for characterizing the radiation patterns and mutual coupling of conformal antennas mounted on a complex platform. This technique uses the higher‐order finite element method (FEM) to model the antennas and the platform and employs the boundary integral equation to terminate the FEM computational domain. The resulting numerical system is solved using a novel preconditioner in conjunction with the multilevel fast multipole algorithm for the fast evaluation of boundary integrals. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 139–142, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10700
Integrated broadband power amplifier/low‐noise amplifier switch for time division diplexer
Authors: Lee Tze Kiu , Chan Wing Shing , Siu Yun Ming
Published: December 2002

When the transmit BJT power amplifier is connected to the receive BJT low‐noise amplifier, a switch can be realized. Since the frequency‐dependant quarter‐wavelength transmission line normally used in low‐cost PIN diode switches has been eliminated, the bandwidth is increased. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 145–147, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10702
Topographic stress perturbations in southern Davis Mountains, west Texas 1. Polarity reversal of principal stresses
Authors: Savage William Z. , Morin Roger H.
Published: December 2002

We have applied a previously developed analytical stress model to interpret subsurface stress conditions inferred from acoustic televiewer logs obtained in two municipal water wells located in a valley in the southern Davis Mountains near Alpine, Texas. The appearance of stress‐induced breakouts with orientations that shift by 90° at two different depths in one of the wells is explained by results from exact solutions for the effects of valleys on gravity and tectonically induced subsurface stresses. The theoretical results demonstrate that above a reference depth termed the hinge point, a location that is dependent on Poisson's ratio, valley shape, and magnitude of the maximum horizontal tectonic stress normal to the long axis of the valley, horizontal stresses parallel to the valley axis are greater than those normal to it. At depths below this hinge point the situation reverses and horizontal stresses normal to the valley axis are greater than those parallel to it. Application of the theoretical model at Alpine is accommodated by the fact that nearby earthquake focal mechanisms establish an extensional stress regime with the regional maximum horizontal principal stress aligned perpendicular to the valley axis. We conclude that the localized stress field associated with a valley setting can be highly variable and that breakouts need to be examined in this context when estimating the orientations and magnitudes of regional principal stresses.
Mapping lateral variations in upper mantle attenuation by stacking P and PP spectra
Authors: Warren Linda M. , Shearer Peter M.
Published: December 2002

We study the lateral variations in P wave attenuation in the upper mantle at frequencies between 0.16 and 0.86 Hz by analyzing the spectra from >18,000 P and >14,000 PP arrivals. We select seismograms from shallow earthquakes at epicentral distances of 40°–80° for P waves and 80°–160° for PP waves. Each spectrum is the product of source, receiver, and propagation response functions as well as local source‐ and receiver‐side effects. We correct each spectrum for average source and attenuation models. Since there are multiple receivers for each source and multiple sources for each receiver, we can approximate the source‐ and receiver‐side terms by stacking the appropriate P log spectra. The resulting source‐specific response functions include any remaining source spectrum and near‐source Q structure; the receiver stacks include the site response and near‐receiver Q structure. We correct the PP log spectra for the appropriate source‐ and receiver‐side stacks. Since attenuation in the lower mantle is small, the residual log spectrum approximates attenuation in the upper mantle near the PP bounce point and is used to estimate δ. We constrain the anomalies to the top 220 km of the mantle, as suggested by previous Q studies, and translate the δ measurements to variations in 1000/Qα. The patterns of more and less attenuating regions generally correlate with previously published shear attenuation models and surface tectonics. Continents are usually less attenuating than the global average, whereas oceanic regions tend to be more attenuating. There are interesting exceptions to this tectonic pattern, such as an attenuating region beneath southern Africa.
Properties of coastal Antarctic aerosol from combined FTIR spectrometer and sun photometer measurements
Authors: Rathke Carsten , Notholt Justus , Fischer Jürgen , Herber Andreas
Published: December 2002

Remotely sensing the physical and chemical properties of summertime aerosol at the Antarctic coastal station Neumayer has been accomplished for the first time by a combined analysis of atmospheric thermal emission spectra, measured by an FTIR spectrometer, and atmospheric visible‐near infrared extinction spectra, measured by a sun photometer. From the synergy of both spectral ranges, we find that the aerosol is composed of 1.1–1.6 mg m−2 of sulfates, with the water component in the solid phase, having a bimodal size distribution with radii peaking at 0.04 and 0.64 μm. We also provide the first estimate of the direct thermal radiative forcing of this aerosol: +1.68 W m−2 at the surface, and +0.006 W m−2 at the top of the atmosphere.
Is high obliquity a plausible cause for Neoproterozoic glaciations?
Authors: Donnadieu Yannick , Ramstein Gilles , Fluteau Frederic , Besse Jean , Meert Joseph
Published: December 2002

The main features of the low‐latitude Neoproterozoic glaciations remain the subject of controversial debates concerning possible triggers. Here we use an AGCM coupled with a slab ocean to test one of the earliest and simplest explanation for tropical glaciations: a higher obliquity of the Earth's rotation axis. We show that high obliquity may result in an extensive glaciation during the Sturtian episode (750 Ma), due to the location of continental masses in the tropical areas, but cannot produce a large glaciation in the case of mid to high latitude paleogeographies such as those thought to typify the Varangian‐Vendian episodes (620–580 Ma).
Is ENSO a cycle or a series of events?
Authors: Kessler William S.
Published: December 2002

After early ideas that saw El Niños as isolated events, the advent of coupled models brought the conception of ENSO as a cycle in which each phase led to the next in a self‐sustained oscillation. Twenty‐two years of observations that represent the El Niño and La Niña peaks (east Pacific SST) and the memory of the system (zonal mean warm water volume) suggest a distinct break in the cycle, in which the coupled system is able to remain in a weak La Niña state for up to two years, so that memory of previous influences would be lost. Similarly, while the amplitude of anomalies persists from the onset of a warm event through its termination, there is no such persistence across the La Niña break. These observations suggest that El Niños are in fact event‐like disturbances to a stable basic state, requiring an initiating impulse not contained in the dynamics of the cycle itself.
A 250‐year high‐resolution record of Pb flux and crustal enrichment in central Greenland
Authors: McConnell Joseph R. , Lamorey Gregg W. , Hutterli Manuel A.
Published: December 2002

Records of contaminant deposition from ice cores document the impact of changing emissions on remote regions. While variations in Greenland ice core Pb concentrations before and after 1970 have been attributed primarily to leaded gasoline emissions, discontinuous coarse sampling in these studies provided limited temporal resolution. Using a continuous, high‐resolution record of Pb and other trace element concentrations from 1750 to 1998, we show that large, sustained increases in Pb deposition in Greenland occurred >50 years before the introduction of leaded gasoline and that non‐gasoline lead contamination likely accounted for >50% of the cumulative increase in lead deposition and crustal enrichment since industrialization. After 1970, mandated emission reductions led to a >75% decline in annual lead flux, with most of the decline occurring from 1970 to 1985. Additional elemental and isotopic tracers will be needed to provide Pb provenance.
Trends in foF2 above Tromsø (69°N 19°E)
Authors: Hall C. M. , Cannon P. S.
Published: December 2002

Regular ionosonde observations from Tromsø (69°N 19°E) date from 1935 and the dataset thus represents one of the longest in existence. Trends in the critical frequency of the ionospheric F2 layer are determined and found to be negative. Our results lend support to a causative mechanism which includes greenhouse cooling.
Evolution of a semicircular flux rope with two ends anchored in the photosphere
Authors: Lin J. , van Ballegooijen A. A. , Forbes T. G.
Published: December 2002

We investigated a coronal magnetic configuration including a semicircular flux rope with two ends anchored in the photosphere. The background field is produced by two source regions on the photosphere. We study the evolution of this configuration in response to the gradual change in the background field, which is modeled by varying either the strength of the source or the distance between the source regions on the photosphere. Our results indicate that the evolution due to the change in source strength shows the likelihood of catastrophic loss of equilibrium, and that the evolution due to the change in the distance is smooth and does not manifest any tendency to lose equilibrium. In the former case, the current sheet starts developing fairly early; it forms even before the evolution reaches the maximum current state. We notice that the effect of the curvature of flux rope on the evolution of the system is significant, such that the equilibrium curve does not form a cusp‐catastrophic structure but a simple fold‐catastrophic structure even if the evolution is ideal MHD and a current sheet attached to the boundary surface occurs. The curvature strengthens the magnetic compression between the flux rope and the photosphere and makes the loss of equilibrium easier. However, the question of how the system behaves after the loss of equilibrium is still open since the flux rope is not likely to remain semicircular at the stage of fast evolution.
Easily monitored entangled state
Authors: Can M. A. , Klyachko A. A. , Shumovsky A. S.
Published: December 2002

We discuss the generation and monitoring of durable atomic entangled state via Raman-type process, which can be used in the quantum information processing.
Growth algorithms for lattice heteropolymers at low temperatures
Authors: Hsu Hsiao-Ping , Mehra Vishal , Nadler Walter , Grassberger Peter
Published: December 2002

Two improved versions of the pruned-enriched-Rosenbluth method (PERM) are proposed and tested on simple models of lattice heteropolymers. Both are found to outperform not only the previous version of PERM, but also all other stochastic algorithms which have been employed on this problem, except for the core directed chain growth method (CG) of Beutler and Dill. In nearly all test cases they are faster in finding low-energy states, and in many cases they found new lowest energy states missed in previous papers. The CG method is superior to our method in some cases, but less efficient in others. On the other hand, the CG method uses heavily heuristics based on presumptions about the hydrophobic core and does not give thermodynamic properties, while the present method is a fully blind general purpose algorithm giving correct Boltzmann–Gibbs weights, and can be applied in principle to any stochastic sampling problem.
Spin relaxation of radicals in low and zero magnetic field
Authors: Fedin M. V. , Purtov P. A. , Bagryanskaya E. G.
Published: December 2002

Spin relaxation of radicals in solution in low and zero magnetic field has been studied theoretically. The main relaxation mechanisms in low magnetic field [modulation of anisotropic and isotropic hyperfine interaction, and modulation of spin–rotational interaction] are considered within a Redfield theory. The analytical results for a radical with one magnetic nucleus (I=12) and for a radical with two equivalent magnetic nuclei (I=12) are obtained and analyzed. It is shown that the probabilities of relaxational transitions in low and zero magnetic fields differ significantly from the probabilities in high magnetic fields. The use of high-field expressions in low and zero magnetic fields is not correct. Taking exact account of spin relaxation is important in calculations of much low-field magnetic resonance data.
Assignment of the complex vibrational spectra of the hydrogenated ZnO polar surfaces using QM/MM embedding
Authors: French S. A. , Sokol A. A. , Bromley S. T. , Catlow C. R. A. , Rogers S. C. , Sherwood P.
Published: December 2002

Hydrogenated zinc oxide gives rise to complex vibrational spectra with many prominent features that remain unexplained. Our calculations have unambiguously shown that the presence of vacant oxygen and zinc interstitial surface sites is the only way to rationalize the observed spectra, notably the 1710 cm−1 zinc hydride stretching mode. The large number of such sites, which expose low-coordinated surface ions, are inherent at ionically reconstructed polar surfaces. The thermal stability of the sorbed hydrogen and the infrared activity of the resulting species are correlated with site coordination and coverage.
Theoretical study of the low-lying electronic states of ruthenium trimer (Ru3)
Authors: Guo Rui , Balasubramanian K.
Published: December 2002

Several low-lying electronic states of the ruthenium trimer (Ru3) were investigated by complete active space multiconfiguration self-consistent field and multireference singles and doubles configuration interaction (MRSDCI) methods that included up to 45 million configurations. Two nearly degenerate states, namely, B111 and B211 states were found as candidates for the ground state at lower level of theory. At the highest MRSDCI level, the B111 state was found to be the ground state of Ru3. The atomization energy of this state was further determined with extensive large-scale MRSDCI calculations. Our calculations facilitate assignment of the recently observed resonance Raman spectra of Ru3 in Ar matrix by Lombardi and co-workers.
Analytic ab initio determination of the elastic modulus in stereoregular polymers: Analytical integral derivatives, long-range effects, implementation, and examples
Authors: Jacquemin Denis , André Jean-Marie , Champagne Benoı̂t
Published: December 2002

An original scheme has been developed to compute, fully analytically, the Hartree–Fock Young modulus (second derivative of the Hartree–Fock energy with respect to the unit cell length) of stereoregular polymers. The evaluation of the elastic modulus is performed without the use of any intercell coordinate. The direct and efficient computation of the Young modulus requires the evaluation of the full Hessian (including cell and mixed components), and, subsequently, some specific integral derivatives and the use of a seven-step coupled-perturbed Hartree–Fock procedure. The long-range effects related to the Young modulus (and other second-order derivatives associated with vibrational frequencies) are evaluated by using a technique based on multiple Taylor expansions. The implementation of the integral derivatives in the McMurchie and Davidson framework is described in detail. Two examples show that the stability and accuracy of the technique proposed are excellent.
Extended rotational diffusion and dielectric relaxation of symmetrical top molecules in a dc electric field
Authors: Titov S. V. , Kalmykov Yu. P. , Coffey W. T.
Published: December 2002

The longitudinal and transverse components of the dielectric susceptibility tensor are calculated for a system of noninteracting symmetrical top molecules subjected to a strong dc electric field. The calculations are carried out using the extended rotational-diffusion model (J-diffusion). The model predicts a strong dependence of the dielectric spectra on the strength of the dc bias field and on the shape of the molecule. Moreover, the dielectric relaxation behavior at low frequencies (ωτγ⩽1, where τγ is the orientation correlation time) is reproduced and the inclusion of inertial effects ensures that optical transparency is regained at very high frequencies (in the far infrared region).
Structure of molten 1,3-dimethylimidazolium chloride using neutron diffraction
Authors: Hardacre Christopher , Holbrey John D. , McMath S. E. Jane , Bowron Daniel T. , Soper Alan K.
Published: December 2002

The model room temperature ionic liquid, 1,3-dimethylimidazolium chloride, has been studied by neutron diffraction for the first time. The diffraction data are used to derive a structural model of this liquid using Empirical Potential Structure Refinement. The model obtained indicates that significant charge ordering is present in the liquid salt and that the local order in this liquid closely resembles that found in the solid state. As in the crystal structure, hydrogen-bonding interactions between the ring hydrogens and the chloride dominate the structure. The model is compared with the data reported previously for both simple alkyl substituted imidazolium halides and binary mixtures with AlCl3.
Ab initio study of the spectroscopy of AgI: A complete active space self-consistent field+averaged coupled pair functional approach to the lowest excited states
Authors: Ramı́rez-Solı́s A.
Published: December 2002

The seven lowest-lying singlet and triplet (X and 2 1Σ+ states, the first Σ+3, Π3,1, and Δ3,1) electronic states of AgI were studied through extensive complete active space self-consistent field+averaged coupled pair functional calculations, with relativistic effective core potentials and optimized Gaussian basis sets for both atoms. The 2 1Σ+ and Σ+3 states show relative minima very near the equilibrium geometry of the ground state, while the former also has another minimum around 8.1 a.u. and is attractive up to 20 a.u. The lowest Π1 state was found to be totally repulsive. The Δ3,1 and Π3 states present very shallow minima, around 5.2 a.u. for the Δ states and at 7.4 a.u. for the Π3 state. The calculated spectroscopic constants for the ground and excited states are compared with the available experimental data and results are discussed in light of the known spectroscopy of the other silver halides. Even though the Π3 state is mostly repulsive, it is almost degenerate with the 2 1Σ+ one near the equilibrium geometry of the ground state, and lies within 4500 cm−1 from the latter in the 5–9 a.u. range, thus a strong 2 1Σ+–3Π mixture through the spin–orbit interaction is predicted to occur that will lead to the fine-structure (0+) single B state (dominated by the 2 1Σ+ component), recently Rydberg–Klein–Rees fitted to explain the revised B←X transitions [Stueber et al., J. Chem. Phys. 109, 9831 (1998)]. These results unequivocally assign the A←X transition as arising from Σ+3←X 1Σ+. In this way accurate spectroscopic data have been derived that lead to new assignments and predictions for electronic states unobserved so far.
Computer modeling of the liquid–vapor interface of an associating Lennard-Jones fluid
Authors: Alejandre José , Duda Yurko , Sokołowski Stefan
Published: December 2002

Monte Carlo and molecular dynamics methods have been used to investigate the influence of chemical association on the structure and thermodynamic properties of the liquid–vapor interface of dimerizing Lennard-Jones fluids. The molecular dynamics simulations have been carried out to obtain the surface tension for the so-called pseudo-mixture model of an associating fluid. The simulation data are also compared with the results of theoretical calculations, based on a density functional approach.