bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of the characteristics of a viscoelastic material from creep analysis using the universal viscoelastic model. I. Isolation of the elastic component designated as the “Projected Elastic Limit”
Authors: Sudduth Richard D.
Published: June 2003

In a preceding publication this author introduced a new universal viscoelastic model to describe a definitive relationship between constant strain rate, creep, and stress relaxation analysis for viscoelastic polymeric compounds. One extremely important characteristic of this new model is that it also characterizes secondary creep very well. Because secondary creep is the linear portion of creep after the completion of primary creep, then a straight line with a slope and an intercept can describe secondary creep. To effectively define a straight line in the secondary creep region it was found necessary to obtain averages of the instantaneous slope and the instantaneous intercept strain by averaging over a series of equally spaced data points in the secondary slope region. Most importantly, this average intercept strain was found to be independent of creep stress and creep time. This means that all the secondary creep straight lines must pass through the same intercept creep strain for all creep stresses. The results presented in this study strongly indicate that this secondary creep intercept strain is independent of creep stress and creep time, and appears to increase as the value of the efficiency of yield energy dissipation decreases. Because a decrease in the efficiency of yield energy dissipation, n, appears to correlate with an increase in the elastic solid like character of a material, then it appears that this secondary creep intercept strain should be a direct measure of the strain that the material can survive to retain its full elastic character. Therefore, this secondary creep intercept strain has been designated as the “Projected Elastic Limit” of a given viscoelastic material. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2923–2936, 2003
Role of heat transfer and thermal conductivity in the crystallization behavior of polypropylene‐containing additives: A phenomenological model
Authors: Radhakrishnan S. , Sonawane Pradip S.
Published: June 2003

The thermal conductivity of a filler and the thermal conductivity of a composite made from that filler influence the heat‐transfer process during melt processing. The heat‐transfer process from the melt to the mold wall becomes an important factor in developing the skin–core morphology. These aspects were examined in this study. The thermal conductivity of polypropylene–filler composites was estimated with a standard model for various fillers such as calcium carbonate, talc, silica, wollastonite, mica, and carbon fibers. The rate of cooling under given conditions, including the melting temperature, mold wall temperature, mass of the composite, and filler content, was estimated with standard heat‐transfer equations. The time to attain the crystallization temperature for polypropylene was evaluated with a regression method with differential temperature steps. The crystallization curves were experimentally determined for the different fillers, and from them, the induction period for the onset of crystallization was estimated. These observations were correlated with the expected trends from the aforementioned formalism. The excellent fit of the curves showed that in all these cases, the thermal conductivity of the filler and composite played a dominant role in controlling the onset of the crystallization process. However, the nucleation effects became important in the later stages after the crystallization temperature was attained. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2994–2999, 2003
Flame retardant flexible poly(vinyl chloride) compound for cable application
Authors: Tian Chunming , Wang Hai , Liu Xiulan , Ma Zhiguang , Guo Huazhi , Xu Jianzhong
Published: June 2003

ZnO/MgO, ZnO/CaO, and ZnO/CaO/MgO can form solid solutions. The solid solution for we as flame retardant (SSFR) was obtained by annealing at 1023 K for 4.5 h in a muffle furnace. Flexible poly (vinyl chloride) (PVC) filled with SSFR and Sb2O3 was investigated by differential thermal analysis thermogravimetry. Limiting oxygen index (LOI), mechanical properties, and electrical properties were studied. The surface of the char formed after combusting of the PVC compounds was observed through scanning electron microscopy and the effect of the surface area to the LOI was also studied. The data suggested that a small amount of SSFR and Sb2O3 have good synergy and can greatly increase the LOI and the char yield, and that the thermal degradation temperature and the activation energy decreased. It can be concluded that the mechanism of SSFR is a condensed‐phase mechanism. Moreover, one can conclude that the surface area can enhance the LOI. All the results showed that SSFR is effective and safe as a flame retardant in flexible PVC. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3137–3142, 2003
Conformation of polyacrylamide in aqueous solution with interactive additives and cosolvents
Authors: Wu Shuhui , Shanks Robert A.
Published: June 2003

The viscosity of polyacrylamide (PAM) dilute aqueous solutions with NaCl, glucose, and SDS as additives was measured by Ubbelohde viscometry. There was linear relationship between reduced viscosity vs. PAM concentration in aqueous solutions. The Huggins constantkand intrinsic viscosity [η] were used to study the conformation of the polymer chains and the degree of polymer–solvent interaction. In addition, the viscosity of diluted PAM solutions in water with acetone, ethanol, DMF, and ethylene glycol as cosolvent was measured. It was found that the polymer chain conformation contracted as the acetone, ethanol, and DMF cosolvent composition ratio increased, but there was no distinguishing difference between water–ethylene glycol compositions. The solution properties of PAM were used to estimate the swelling properties of PAM gel in the same external conditions, as gel is formed by crosslinking of linear polymer. In good solvent the polymer chain should be expanded, and gel is expected to have large swelling ratio. In water cosolvent systems, when the linear polymer chain underwent coil–globule transition, PAM gel should have volume phase transition under corresponding external conditions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3122–3129, 2003
Synthesis of novel chiral Cu or Ag/S,N cluster complexes and absolute stereostructures as determined by x‐ray crystallography
Authors: Shi Min , Jiang Jian‐Kang
Published: June 2003

Novel chiral copper(I) and silver(I) metal complexes were synthesized from the reaction of chiral 1,3‐thiazolidine‐2‐thione ligand with CuCl and AgOAc in dichloromethane in the presence of Et3N and DMAP at room temperature. Their unique crystal structures were determined by X‐ray analysis. Four Cu(I) atoms and four 1,3‐thiazolidine‐2‐thione ligands form a butterfly‐type metal cluster. Six Ag(I) atoms and six 1,3‐thiazolidine‐2‐thione ligands form another butterfly‐type cluster. Chirality 15:605–608, 2003. © 2003 Wiley‐Liss, Inc.
Evaluation of a ristocetin bonded stationary phase for subcritical fluid chromatography of enantiomers
Authors: Lavison Gwenaelle , Thiébaut Didier
Published: June 2003

A stationary phase derived from ristocetin was evaluated for chiral separation in subcritical fluid chromatography. Separation of various enantiomers having different structures and pKa values were investigated using carbon dioxide and polar modifiers. The influence of modifiers, additives, temperature, and mobile phase flow rate on separations is presented. It is concluded that this stationary phase can be used for SFC despite its structural similarity with protein‐derived stationary phases that can only be used in HPLC. The separation mechanisms could not be elucidated or predicted using these initial experiments. The separations of warfarin and, especially, efavirenz demonstrate the potential of this type of stationary phase for rapid SFC chiral separations. Chirality 15:630–636, 2003. © 2003 Wiley‐Liss, Inc.
Manifestation of chiral recognition of camphor enantiomers by α‐cyclodextrin in longitudinal and transverse relaxation rates of the corresponding 1:2 complexes and determination of the orientation of the guest inside the host capsule
Authors: Anczewski Waldemar , Dodziuk Helena , Ejchart Andrzej
Published: June 2003

The 1:2 complexes of camphor enantiomers with α‐cyclodextrin in 2H2O manifest differences in longitudinal and transverse relaxation rates of camphor methyl protons owing to chiral recognition. The relaxation data obtained at two magnetic fields were quantitatively analyzed using the model of anisotropic overall tumbling with internal motion. In experimental conditions (guest‐to‐host ratio = 1:20, T = 300.6K), all camphor molecules are complexed. The complexes are not rigid but the rotational diffusion of camphor enantiomers embedded inside the capsules formed by two α‐cyclodextrin hosts is well outside the extreme narrowing region. Both differences in the anisotropic overall tumbling and internal rotation of all methyl groups participate in enantiomeric differentiation of the relaxation rates. Anisotropic tumbling of camphor molecules provides information on the orientation of the guest in the host capsule that for the complex under study could not be obtained by other methods. Chirality 15:654–659, 2003. © 2003 Wiley‐Liss, Inc.
Local corona behavior and creeping discharge on (needle‐dielectric, semiconductor) composite electrodes
Authors: Sakamoto Naoki , Kuninaka Yoshito , Ueno Hideki , Nakayama Hiroshi
Published: June 2003

This paper describes local corona behavior and creeping discharge on composite electrode systems in N2. The composite electrode consisted of a needle contacted with a borosilicate glass or a ZnO disk on a needle–plane configuration. The discharge voltages increased when the needle was in contact with the glass with increasing creeping distance (L) from the needle tip to the bottom of the disk. The discharge voltages showed a reversed polarity effect beginning at L = 4 mm. In the case of a needle in contact with ZnO, the discharge voltage increased with distance until L = 2 mm, but decreased beyond L = 2 mm. Observation using an ultrahigh‐speed camera showed that the discharge behavior was different for the glass and for the ZnO. Corona photographs taken by a camera with an image intensifier showed that the corona was generated at the triple junction in the case of ZnO. The differences in discharge voltage characteristics and the discharge behavior between the glass and ZnO were associated with the corona properties. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(1): 1–9, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10208
Age–period–cohort models and disease mapping
Authors: Lagazio Corrado , Biggeri Annibale , Dreassi Emanuela
Published: June 2003

Joint modelling of space and time variation of the risk of disease is an important topic in descriptive epidemiology. Most of the proposals in this field deal with at most two time scales (age–period or age–cohort). We propose a hierarchical Bayesian model that can be used as a general framework to jointly study the evolution in time and the spatial pattern of the risk of disease. The rates are modelled as a function of purely spatial terms (local effects of risk factors that do not vary in time), time effects (on the three time axes: age, calendar period and birth cohort) and space–time interactions that describe area specific time patterns. Copyright © 2003 John Wiley & Sons, Ltd.
Deleterious effects of mild simulated overwintering temperatures on survival and potential fecundity of rose‐galling Diplolepis wasps (Hymenoptera: Cynipidae)
Authors: Williams Jason B. , Shorthouse Joseph D. , Lee Richard E.
Published: June 2003

Prepupae of the rose galling Diplolepis spinosa from areas with relatively cold winters in southern Canada, and Diplolepis variabilis from a milder locale in western Canada, were used to test the hypothesis that mild winter temperatures are detrimental to the survival and potential fecundity of insects. Prepupae of D. spinosa held within or removed from their galls were exposed to simulated overwintering temperatures (−22, 0, 5, or 10°C) for approximately four months before measuring their survival, body size, and potential fecundity. Similar studies were conducted using prepupae of D. variabilis that were removed from their gall and subjected to 0°C or 10°C treatments. Diplolepis spinosa, with or without their galls, averaged 66% more mortality at 10°C than at 0°C. Female D. spinosa that survived the 10°C treatment had 32% fewer eggs than those held at 0°C. In contrast, there was no difference in survival or numbers of eggs between D. variabilis held at 0°C and 10°C. Body size of adult females and size of eggs did not differ among temperature treatments for either species. We conclude that mild overwintering temperatures may be detrimental for insects by raising their metabolism, and consequently reducing energetic reserves needed for development to the adult stage and subsequent production of eggs the following spring. J. Exp. Zool. 298A:23–31, 2003. © 2003 Wiley‐Liss, Inc.
Effects of acid stress in adult Rana pipiens
Authors: Brodkin Marc , Vatnick Itzick , Simon Martin , Hopey Hollyann , Butler‐Holston Kristine , Leonard Michelle
Published: June 2003

The decline in frog populations is a well‐recognized worldwide phenomenon and infectious disease has been implicated as a major cause in the global decline of amphibian populations. Rana pipiens are disappearing from many habitats where they used to flourish, and environmental acidification has been considered as a possible contributor to this disappearance. We present a model that integrates the results of several experiments on the effects of acid exposure on natural resistance and mortality of adult Rana pipiens. These studies suggest that different components of the natural defense mechanisms of these frogs have different acid sensitivities. We have shown previously that exposure to pH 5.5 leads to a reduction in splenic white blood cell number, viability, and to colonization of the spleen with both Gram positive and Gram negative bacteria. In this paper we show that exposure to pH 6.0 did not affect the number or viability of splenic white blood cells but did result in colonization of the spleen by bacteria. We also show that cold exposure by itself does not cause a systemic bacterial infection in adult Rana pipiens, but acid stress following cold exposure does. The data presented in this paper provide empirical evidence to support the hypothesis that acid stress may be a contributor to the decline of Rana pipiens in the northeastern region of the United States. J. Exp. Zool. 298A:16–22, 2003. © 2003 Wiley‐Liss, Inc.
A printed ultra‐wideband diversity monopole antenna
Authors: Wong Kin‐Lu , Su Saou‐Wen , Kuo Yen‐Liang
Published: June 2003

A novel ultra‐wideband (UWB) diversity monopole antenna printed on a personal computer memory card international association (PCMCIA) network card is presented. The antenna consists of two truncated square monopoles orthogonally and symmetrically printed on the two sides of a T‐shaped protruded ground plane, and is capable of operating in a very wide bandwidth, defined by a 10‐dB return loss, of about 5.4 GHz (about 2.3–7.7 GHz). In addition, across the operating bandwidth, the antenna also shows good port isolation (S21 < −20 dB) and can provide spatial diversity for the obtained radiation patterns of the two truncated square monopoles which substantially cover complementary space regions. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 257–259, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11031
Analysis of 3D frequency‐selective structures using a high‐order finite‐element method
Authors: Lou Zheng , Jin Jian‐Ming
Published: June 2003

A high‐order vector finite‐element method (FEM) is presented for the analysis of 3D frequency‐selective structures (FSSs). The asymptotic waveform evaluation (AWE) technique is combined with the FEM to perform fast frequency and angular sweeps. Reflection/transmission characteristics of several frequency‐selective structures are calculated and compared with the existing results. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 259–263, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11032
BIT error rate and noise inS‐band TDFA‐amplified 10‐Gb/s optical transmission
Authors: Bessa dos Santos A. , Costa e Silva M. B. , Carvalho M. T. , Sundheimer M. L. , Gomes A. S. L. , von der Weid J. P.
Published: June 2003

We report on the measurements and calculations of bit error rate (BER) and noise figure (NF) in an up‐conversion‐pumped thulium‐doped fiber amplifier for theSband. Error‐free transmission (BER < 10−9) was achieved, and good agreement between measured and calculated power penalties was obtained. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 277–279, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11037
Full‐wave FDTD design and analysis of wideband microstrip‐to‐waveguide transitions
Authors: Reig Càndid , Navarro Enrique A. , Such Vicente
Published: June 2003

Wideband transitions are designed and analysed by using two different approaches of the finite‐difference time‐domain (FDTD) method, in combination with the theory of nonuniform transmission lines. These transitions consist of a ridged waveguide‐based taper between a shielded microstrip and a standard X‐band rectangular waveguide. In the first step, a full‐wave 2D‐FDTD scheme is used to calculate the dispersion characteristics, as well as the geometry dependence of the impedance in the double ridged waveguide. Once these design curves have been obtained, the stepped transmission line transformer theory is used to design the tapers. In a former step, the nonuniform 3D‐FDTD technique is applied, the transitions are simulated and the method is validated. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 317–320, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11048
Sleeve monopole antennas at the center of a circular ground plane
Authors: Guo Jingli , Ji Yicai , Liu Qizhong
Published: June 2003

A new moment method is presented to analyze sleeve monopole antennas at the center of a circular ground plane. The input impedance and radiation pattern of the antenna are calculated. Good agreement between the computed and measured results is obtained. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 341–343, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11055
Isolation and culture of embryonic stem cells from porcine blastocysts
Authors: Li Ming , Zhang Dong , Hou Yi , Jiao Lihong , Zheng Xing , Wang Wei‐Hua
Published: June 2003

This study was conducted to establish embryonic stem (ES) cell lines from porcine blastocysts. Blastocysts were collected from China miniature pigs at day 7–9 of pregnancy. Embryos were either directly (intact embryos) cultured on mitomysin C‐inactivated murine embryonic fibroblasts (MEF) as feeder layers, or were used to isolate the inner cell masses (ICM) by enzyme digestive method and then cultured. It was found that enzyme digestive method could isolate ICMs without any damages of cells in all blastocysts (28). All ICMs attached to the feeder layers. Primary cell colonies were formed in 68% of ICM culture and 28% of intact blastocyst culture. Two ES cell lines derived from ICM passed six subcultures (passages). These cells morphologically resembled mouse ES cells and consistently expressed alkaline phosphatase activity. When the ES cells were cultured in a medium without feeder layer and leukemin inhibitory factor, they differentiated into several types of cells including neuron‐like, smooth muscle‐like, and epithelium‐like cells. Some cells formed embryoid bodies in a suspension culture. These results indicate that porcine ES cell line can be established under the present experimental conditions and these ES cells are pluripotent. Mol. Reprod. Dev. 65: 429–434, 2003. © 2003 Wiley‐Liss, Inc.
Birth of germline chimeras by transfer of chicken embryonic germ (EG) cells into recipient embryos
Authors: Park Tae Sub , Hong Yeong Ho , Kwon Se Chang , Lim Jeong Mook , Han Jae Yong
Published: June 2003

This study reports for the first time the production of chicken germline chimeras by transfer of embryonic germ (EG) cells into recipient embryos of different strain. EG cells were established by the subculture of gonadal tissue cells retrieved from stage 28 White Leghorn (WL) embryos with I/I gene. During primary culture (P0), gonadal primordial germ cells (gPGCs) in the stromal cells began to form colonies after 7 days in culture with significant (P < 0.0001) increase in cell population. Colonized gPGCs were then subcultured with chicken embryonic fibroblast monolayer for EG cell preparation. Prepared EG cells or gPGCs at P0 were transferred to stage 17 Korean Ogol chicken (KOC) embryos with i/i gene. The recipient chickens were raised for 6 months to sexual maturity, then a testcross analysis by artificial insemination was conducted for evaluating germline chimerism. As results, transfer of EG cells and gPGCs yielded total 17 germline chimeras; 2 out of 15 (13.3%) and 15 of 176 sexually matured chickens (8.5%), respectively. The efficiency of germline transmission in the chimeras was 1.5–14.6% in EG cells, while 1.3–27.6% in gPGCs. In conclusion, chicken germline chimeras could be produced by the transfer of EG cells, as well as gPGCs, which might enormously contribute to establishing various innovative technologies in the field of avian transgenic research for bioreactor production. Mol. Reprod. Dev. 65: 389–395, 2003. © 2003 Wiley‐Liss, Inc.
Degree of sex reversal as related to plasma steroid levels in genetic female chickens (Gallus domesticus) treated with fadrozole
Authors: Vaillant S. , Guémené D. , Dorizzi M. , Pieau C. , Richard‐Mercier N. , Brillard J.‐P.
Published: June 2003

The objectives of this work were to determine whether or not plasma levels of testosterone and estradiol reflect the various grades of sex reversal in genetic female chickens treated with Fadrozole (CGS 16949 A), a nonsteroidal aromatase inhibitor, and whether gonadal aromatase activity and plasma levels of testosterone and estradiol in treated females can or not be modified by post‐hatch treatments with Fadrozole or Fadrozole + testosterone. Eggs were injected with 1 mg Fadrozole on day 4 of incubation. In females having developed sex‐reversed gonads, endocrine parameters (estradiol and testosterone) at and after 13 weeks of age were indicative of the degree of sex reversal, with, for example, sex‐reversed females with two testes having the highest levels of testosterone and the lowest levels of estradiol. Among these females, eight (from a total of 13) produced ejaculates with scarce and abnormal spermatozoa. Some motility was observable in the ejaculates from five of them. None of the post‐hatch treatments had a significant effect on plasma levels of testosterone or estradiol (measured at 3‐week intervals from week 4 to week 28 post‐hatch) or on gonadal aromatase activity (measured at 12 and 28 weeks). In conclusion, these results indicate that plasma levels of testosterone and estradiol at and after 13 weeks of age are valuable indicators of the degree of sex reversal in female chickens treated with Fadrozole prior to gonadal sex differentiation. In pre‐cited conditions, post‐natal treatments with either Fadrozole or Fadrozole + testosterone had no apparent effect on the degree of sex reversal in these birds. Finally, the occurrence of ejaculates with motile although scarce and abnormal spermatozoa, revealed that epididymes and ducti deferens can develop and become functional in sex‐reversed female chickens. Mol. Reprod. Dev. 65: 420–428, 2003. © 2003 Wiley‐Liss, Inc.
Mixed finite element approximation of an MHD problem involving conducting and insulating regions: The 3D case
Authors: Guermond J. L. , Minev P. D.
Published: June 2003

In this paper we extend in 3D a 2D Lagrange finite element technique proposed previously in Guermond and Minev (Mod. Math. Anal. Num. 2001) for solving the Maxwell equations in the low‐frequency limit in a domain composed of conducting and insulating regions. © 2003 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 19: 709–731, 2003.
Motives for foreign direct investment in Oman
Authors: Mellahi K. , Guermat C. , Frynas J. G. , Al‐Bortmani H.
Published: June 2003

This paper empirically examines the factors that influence foreign investors to engage in foreign direct
investment (FDI) in Oman. One hundred and six foreign equity ventures participated in the study. The
analysis of the data reveals that political and economic stability are the two most important motives for
investing in Oman. Contrary to expectations, purchasing power of customers, market size, and availability of
low‐cost inputs are the least desirable factors, respectively. The statistical analysis indicates that
all motives do not equally appeal to all foreign investors from different countries. © 2003 Wiley
Periodicals, Inc.
A Sco homologue plays a role in defence against oxidative stress in pathogenic Neisseria
Authors: Seib Kate L , Jennings Michael P , McEwan Alastair G
Published: June 2003

Sco proteins are found in mitochondria and in a variety of oxidase positive bacteria. Although Sco is required for the formation of the CuA centre in a cytochrome oxidase of the aa
3 type, it was observed that oxidases with a CuA centre are not present in many bacteria that contain a Sco homologue. Two bacteria of this type are the pathogens Neisseria meningitidis and Neisseria gonorrhoeae. The sco genes of N. gonorrhoeae strain 1291 and N. meningitidis strain MC58 were cloned, inactivated by inserting a kanamycin resistance cassette and used to make knockout mutants by allelic exchange. Both N. gonorrhoeae and N. meningitidis sco mutants were highly sensitive to oxidative killing by paraquat, indicating that Sco is involved in protection against oxidative stress in these bacteria.
LKB1, a protein kinase regulating cell proliferation and polarity
Authors: Boudeau Jérôme , Sapkota Gopal , Alessi Dario R.
Published: June 2003

LKB1 is a serine‐threonine protein kinase mutated in patients with an autosomal dominantly inherited cancer syndrome predisposing to multiple benign and malignant tumours, termed Peutz–Jeghers syndrome. Since its discovery in 1998, much research has focused on identification and characterisation of its cellular roles and analysing how LKB1 might be regulated. In this review we discuss exciting recent advances indicating that LKB1 functions as a tumour suppressor perhaps by controlling cell polarity. We also outline the current understanding of the molecular mechanisms by which LKB1 is regulated in vivo, through interaction with other proteins as well as by protein phosphorylation and prenylation.
Small GTPase ‘Rop’: molecular switch for plant defense responses
Authors: Agrawal Ganesh K. , Iwahashi Hitoshi , Rakwal Randeep
Published: June 2003

The conserved Rho family of GTPases (Rho, Rac, and Cdc42) in fungi and mammals has emerged as a key regulator of diverse cellular activities, such as cytoskeletal rearrangements, programmed cell death, stress‐induced signaling, and cell growth and differentiation. In plants, a unique class of Rho‐like proteins, most closely related to mammalian Rac, has only been found and termed ‘Rop’ (Rho‐related GTPase from plant [Li et al. (1998) Plant Physiol. 118, 407–417; Yang (2002) Plant Cell 14, S375–S388]). ROPs have been implicated in regulating various plant cellular responses including defense against pathogens. It has been shown that ROPs, like mammalian Rac, trigger hydrogen peroxide production and hence the ‘oxidative burst’, a crucial component associated with the cell death, most likely via activation of nicotinamide adenine dinucleotide phosphate oxidase in both monocotyledonous and dicotyledonous species. Recent studies have established that ROPs also function as a molecular switch for defense signaling pathway(s) linked with disease resistance. As discerning the defense pathway remains one of the priority research areas in the field of plant biology, this review is therefore particularly focused on recent progresses that have been made towards understanding the plant defense responses mediated by ROPs.
Muscle FBPase in a complex with muscle aldolase is insensitive to AMP inhibition
Authors: Rakus D. , Pasek M. , Krotkiewski H. , Dzugaj A.
Published: June 2003

Real‐time interaction analysis, using the BIAcore biosensor, of rabbit muscle FBPase–aldolase complex revealed apparent binding constant [K
Aapp] values of about 4.4×108 M−1. The stability of the complex was down‐regulated by the glycolytic intermediates dihydroxyacetone phosphate and fructose 6‐phosphate, and by the regulator of glycolysis and glyconeogenesis – fructose 2,6‐bisphosphate. FBPase in a complex with aldolase was entirely insensitive to inhibition by physiological concentrations of AMP (I
0.5 was 1.35 mM) and the cooperativity of the inhibition was not observed. The existence of an FBPase–aldolase complex that is insensitive to AMP inhibition explains the possibility of glycogen synthesis from carbohydrate precursors in vertebrates’ myocytes.
Non‐hydrolyzable analog of GTP induces activity of Na+ channels via disassembly of cortical actin cytoskeleton
Authors: Shumilina Ekaterina V , Khaitlina Sofia Yu , Morachevskaya Elena A , Negulyaev Yuri A
Published: June 2003

The role of G proteins in regulation of non‐voltage‐gated Na+ channels in human myeloid leukemia K562 cells was studied by inside‐out patch‐clamp method. Na+ channels were activated by non‐hydrolyzable analog of guanosine triphosphate (GTP), GTPγS, known to activate both heterotrimeric and small G proteins. Channel activity was not affected by aluminum fluoride that indiscriminately activates heterotrimeric G proteins. The effect of GTPγS was prevented by phalloidin and by G‐actin, both interfering with actin disassembly, which indicates that GTPγS‐induced channel activation was likely due to microfilament disruption. GTPγS‐activated channels were inactivated by polymerizing actin. These data show, for the first time, that small G proteins can regulate Na+ channels, and an intracellular mechanism mediating their effect involves actin cytoskeleton rearrangements.
SAP97 increases Kv1.5 currents through an indirect N‐terminal mechanism
Authors: Eldstrom Jodene , Choi Woo Sung , Steele David F , Fedida David
Published: June 2003

The functional interaction of the voltage‐gated potassium channel hKv1.5 with the PDZ domain containing protein SAP97 has been investigated. In marked contrast with the known dependence of SAP97‐induced Kv1 potassium current down‐regulation on the channel C‐termini, SAP97 increased hKv1.5 current through an indirect interaction with the Kv1.5 N‐terminus. Deletion of the Kv1.5 N‐terminus eliminated the SAP97‐mediated increase in potassium currents whereas deletion of the channel's C‐terminal PDZ binding motif had no effect. In contrast with other Kv1–SAP97 interactions, no physical interaction could be detected in vivo or in vitro between the two proteins. The proteins did not co‐localize in cardiac myocytes nor did they co‐immunoprecipitate from transfected HEK cells. Yeast two‐hybrid experiments also failed to detect any interaction between the two proteins, but in one experiment of six, Kv1.5 co‐immunoprecipitated very inefficiently with SAP97 from rat ventricular myocytes. Thus, we conclude that the influence of SAP97 on Kv1.5 potassium current levels is dependent upon a novel regulatory mechanism.
A defect in the yeast plasma membrane urea transporter Dur3p is complemented by CpNIP1, a Nod26‐like protein from zucchini (Cucurbita pepo L.), and by Arabidopsis thaliana δ‐TIP or γ‐TIP
Authors: Klebl Franz , Wolf Michael , Sauer Norbert
Published: June 2003

Dur3 encodes the yeast plasma membrane urea transporter and Δdur3 mutants are unable to grow on media containing low concentrations of urea as sole nitrogen source. Complementation of the Δdur3 mutant line with expression libraries generated from whole Arabidopsis thaliana seedlings or from zucchini (Cucurbita pepo L.) vascular tissue yielded numerous lines that had regained the capacity to grow on low urea as sole nitrogen source. Analysis of several of these yeast lines revealed that the Δdur3 mutation was complemented either by δ‐TIP (TIP=onoplast ntrinsic rotein) or γ‐TIP from Arabidopsis or by CpNIP1, a new NOD26‐like protein from zucchini. δ‐TIP (At3g16240) and γ‐TIP (At2g36830) had previously been characterized as proteins facilitating the transport of water across the tonoplast membrane, and Nod26‐like proteins were characterized as glycerol transporters. So far, transport of urea has not been described for any of the proteins described in this paper. Further analyses support this function of TIPs and nodulin 26‐like intrinsic proteins in urea transport.
Apicomplexan parasites contain a single lipoic acid synthase located in the plastid
Authors: Thomsen-Zieger Nadine , Schachtner Joachim , Seeber Frank
Published: June 2003

Apicomplexan parasites contain a vestigial plastid called apicoplast which has been suggested to be a site of [Fe–S] cluster biogenesis. Here we report the cloning of lipoic acid synthase (LipA) from Toxoplasma gondii, a well known [Fe–S] protein. It is able to complement a LipA‐deficient Escherichia coli strain, clearly demonstrating that the parasite protein is a functional LipA. The N‐terminus of T. gondii LipA is unusual with respect to an internal signal peptide preceding an apicoplast targeting domain. Nevertheless, it efficiently targets a reporter protein to the apicoplast of T. gondii whereas co‐localization with the fluorescently labeled mitochondrion was not detected. In silico analysis of several apicomplexan genomes indicates that the parasites, in addition to the presumably apicoplast‐resident pyruvate dehydrogenase complex, contain three other mitochondrion‐localized target proteins for lipoic acid attachment. We also identified single genes for lipoyl (octanoyl)‐acyl carrier protein:protein transferase (LipB) and lipoate protein ligase (LplA) in these genomes. It thus appears that unlike plants, which have only two LipA and LipB isoenzymes in both the chloroplasts and the mitochondria, Apicomplexa seem to use the second known lipoylating activity, LplA, for lipoylation in their mitochondrion.
Radical production from free and peptide‐bound methionine sulfoxide oxidation by peroxynitrite and hydrogen peroxide/iron(II)
Authors: Nakao Lia S , Iwai Leo K , Kalil Jorge , Augusto Ohara
Published: June 2003

Methionine sulfoxide is a post‐translational protein modification that has been receiving increasing attention in the literature. Here we used electron paramagnetic resonance spin trapping techniques to show that free and peptide‐bound methionine sulfoxide is oxidized by hydrogen peroxide/iron(II)‐EDTA and peroxynitrite through the intermediacy of the hydroxyl radical to produce both CH3and CH2CH2CH radicals. The results indicate that methionine sulfoxide residues are important targets of reactive oxygen‐ and nitrogen‐derived species in proteins. Since the produced protein‐derived radicals can propagate oxidative damage, the results add a new antioxidant route for the action of the enzyme peptide methionine sulfoxide reductase.
Over‐expression of Escherichia coli F1Fo–ATPase subunit a is inhibited by instability of the uncB gene transcript
Authors: Arechaga Ignacio , Miroux Bruno , Runswick Mike J. , Walker John E.
Published: June 2003

Little is known about the stability of transcripts encoding membrane proteins in strong expression systems and its effect on membrane protein over‐production. We have expressed all the genes encoding subunits of the membrane domain Fo of the ATP synthase in a T7 RNA polymerase‐based system. All of them but uncB (subunit a) were expressed separately at very high levels in the bacterial hosts Escherichia coli C41(DE3) and C43(DE3). However, expression of uncB was extremely toxic to the bacteria. Northern blot analysis showed that the level of accumulation of the mRNA from uncB was very low. Deletion of uncB in combination with gene fusion experiments demonstrated that the middle region of the gene, encoding amino acids 92–171, exhibited a dominant toxic phenotype associated with a very poor level of expression. Green fluorescent protein fusions with N‐ and C‐ends of uncB helped to stabilize the mRNA and to obtain high yields of protein.
Interaction of EBV latent origin of replication with the nuclear matrix: identification of S/MAR sequences and protein components
Authors: Mearini Giulia , Chichiarelli Silvia , Zampieri Michele , Masciarelli Silvia , D'Erme Maria , Ferraro Anna , Mattia Elena
Published: June 2003

During latency, Epstein Barr virus (EBV) genome, as an episome, is attached to the nuclear matrix (NM) via the latent origin of replication ori P. Within this element, we have found that a region, 580 bp long, encompassing the replicator DS element, shows the strongest affinity for the NM. In addition, by cross‐linking withcis‐diamminedichloroplatinum, we have identified two NM proteins with an apparent molecular weight of 85 and 60 kDa that, with high affinity and specificity, bind ori P. These proteins are not induced by EBV infection, but their interaction with ori P is lost upon induction of EBV lytic cycle. These data strongly suggest that the binding of ori P to specific components of the NM is required for EBV latent replication.
Differential association of the auxiliary subunit Kvβ2 with Kv1.4 and Kv4.3 K+ channels
Authors: Wang Lin , Takimoto Koichi , Levitan Edwin S
Published: June 2003

Kvβ2 subunits associate with Kv1 and Kv4 K+ channels, but the basis of preferential association is not understood. For example, detergent resistance suggests stronger auxiliary subunit association with Kv4.2 than with Kv1.2, but Kvβ2 preferentially localizes with the latter channels in brain. Here we examine the interaction of Kvβ2 with two native binding partners in brain: Kv4.3 and Kv1.4. We show that the auxiliary subunit binds more efficiently to Kv1.4 than to Kv4.3 in mammalian cells. However, preexisting Kvβ2 complexes with Kv1.4 and Kv4.3 have similar detergent sensitivity. Thus, preferential steady state binding may reflect a difference in initial association rather than stability. We also find that that the cytoplasmic C‐terminus of Kv4.3 inhibits Kvβ2 association. Apparently, a region proximal to the Kv4.3 pore contributes to the inefficient auxiliary subunit interaction that produces preferential binding of Kvβ2 to Kv1 channels.
Lead and other metals in gestational hypertension
Authors: Magri J. , Sammut M. , Savona‐Ventura C.
Published: June 2003

Objectives: To identify any effects that lead, calcium, magnesium, and zinc may have on the development of gestational hypertension. Methods: Third‐trimester 110 normotensive and 33 gestational hypertension cases were assayed for various metal levels, using standard techniques, including atomic absorption spectrometry. Results: Gestational hypertension cases showed significantly higher blood lead levels than normotensives. No differences were noticed regarding calcium (ionized and total), magnesium, and zinc levels. Blood lead was significantly related with blood pressure, even after correcting for the body mass indices and age. Blood pressure levels showed no relation to the other analyzed metals. However, the lead:ionized calcium ratio showed a stronger association with blood pressure, than lead alone. Blood lead showed a significant negative relationship with ionized calcium, but none with the other metals. Conclusions: Blood lead evidently influenced blood pressure increments and gestational hypertension development. This implies that all efforts should be made to reduce the population's exposure.
Prediction of the occurrence and intensity of post-traumatic stress disorder in victims 32 months after bomb attack
Authors: Jehel Louis , Paterniti Sabrina , Brunet Alain , Duchet Clara , Guelfi Julien Daniel
Published: June 2003

Introduction

Our objective was to identify factors that predict occurrence and severity of post-traumatic stress disorder (PTSD) after a terrorism attack.

Population

We evaluated 32 victims of a bomb attack in a Paris subway in December 1996 at 6 and 32 months.

Methods

Sociodemographic characteristics, clinical data and physical injuries were used to predict PTSD occurrence and severity in 32 victims. The Watson’s PTSD Inventory (PTSD-I) and the Impact of Event Scale (IES) by Horowitz were used to evaluate occurrence and severity of PTSD, respectively.

Results

Thirty-nine percent of participants met PTSD criteria at 6 months, 25% still had PTSD at 32 months. Women had PTSD 32 months after the bomb attack more frequently than men. Employment predicted PTSD severity at 32 months. PTSD scores assessed by PTSD-I at 6 months were significantly and positively associated with IES scores at 32-month follow-up (r= 0.55,P= 0.004). Psychotropic drug use before the bomb attack significantly predicted PTSD occurrence and severity at 6 and 32 months. In a linear regression model, physical injuries, employment status and psychotropic drug use before the bomb attack were independent predictors of severity of PTSD at 32 months.

Conclusions

Bomb attack exposure resulted in persisting PTSD in a significant proportion of victims; the severity was predicted at 32 months by physical injuries and psychotropic drug use before the terrorism attack and by the PTSD score few months after the bomb attack.
The relevance of suicidal behaviour in jail and prison suicides
Authors: Fruehwald Stefan , Frottier Patrick , Matschnig Teresa , Eher Reinhard
Published: June 2003

Purpose

Suicide rates in correctional institutions have been increasing during the last decades. There has been little interest in whether suicidal ideation and intent has been documented by non-medical prison staff (reports of attempted suicide, suicide threats, self-harm), and whether these signs of suicidality had the consequence of adequate intervention efforts.

Methods

The personal files of inmates who committed suicide in the 29 Austrian jails and prisons during the last 25 years (1975–1999) were included. We analysed personal characteristics, criminological data, circumstances of custody and information about psychiatric disorders and treatment.

Results

Of a total of 250 suicides, 220 personal files were available and included. Suicide attempts were known in 50% of all suicides and 37% had expressed suicidality. In >20%, non-medical staff had documented signs of suicidality, but no further preventive action (e.g. referral to psychiatric care) had taken place.

Conclusions

Signs of suicidality play an important role in vulnerability profiles for jail and prison suicides and should have the minimal consequence of further psychiatric care.
A fisheries application of a dual-frequency identification sonar acoustic camera
Authors: Moursund Russell A , Carlson Thomas J , Peters Rock D
Published: June 2003

The uses of an acoustic camera in fish-passage research at hydropower facilities are being explored by the U.S. Army Corps of Engineers. The “Dual-Frequency Identification Sonar” (DIDSON) is a high-definition imaging sonar that obtains near-video quality images for the identification of objects underwater. Developed originally for the U.S. Navy by the University of Washington's Applied Physics Laboratory, it bridges the gap between existing fisheries-assessment sonar and optical systems. The images within 12 m of this acoustic camera are sufficiently clear such that fish can be observed undulating as they swim and their orientation ascertained in otherwise zero-visibility water. In the 1.8 MHz high-frequency mode, this system 96 beams over a 29° field-of-view. The high resolution and fast frame rate provide target visualization in real time. The DIDSON can be used where conventional underwater cameras would be limited by low light levels and high turbidity.
Results of experiments on the video-acoustic estimation of fish target strength in situ
Authors: Ermolchev Viatcheslav A , Zaferman Michael L
Published: June 2003

Present methods for determining the target strength (TS) of fish do not meet the requirements of accuracy, since they are not provided with reliable working standards and therefore have no correct metrological basis. Attempts to develop such a basis by means of catch analysis have not brought good results, because any fishing gear is selective, and TS measurements of single fish in situ are uncertain when data on their length distribution and behaviour are lacking. To overcome this difficulty, the Knipovich Polar Research Institute of Marine Fisheries and Oceanography (PINRO) has been developing a video-acoustic method to measure TS of fish in situ. The method involves the processing of two independent data flows from the same fish received synchronously through the acoustic and video channels. Good matching of the effective ranges of both channels can be achieved by maximizing the underwater visibility range of the video camera. To this end, the laser underwater television system (LTV) was used. Field experiments showed the visibility range of the LTV to be 3.2 times that of the ordinary underwater video.
Modelling the acoustic effect of swimbladder compression in herring
Authors: Gorska Natalia , Ona Egil
Published: June 2003

Obtaining accurate data on fish target strength (TS) is important when determining the quality of the results from acoustic surveys. However, this requires an improved understanding of both behavioural and environmental influences on the acoustic backscattering by fish. It is well known that the increased pressure with depth compresses the swimbladder of herring, and it has been confirmed by in situ measurements that the TS of adult herring (30–34 cm) is 3–5 dB weaker at 300 m than that of fish close to the surface. Understanding exactly how swimbladder compression may influence herring TS is, therefore, of great interest, and is the main motivation behind this study. Taking account of swimbladder volume changes with depth, we obtained analytical solutions using the Modal-Based, Deformed-Cylinder Model (MB-DCM). The mean-backscattering cross-section is then computed with selected orientation patterns, length distributions, and contrast parameters. The depth-dependence of TS at different acoustic frequencies has been studied. We conducted a sensitivity analysis to show how TS is dependent on the contraction rates of the bladder dimensions and on the fish-orientation distribution. Our theoretical results are compared with TS measured at 38 kHz.
Acoustic scattering by an arbitrarily shaped body: an application of the boundary-element method
Authors: Okumura Tsuyoshi , Masuya Toshikazu , Takao Yoshimi , Sawada Kouichi
Published: June 2003

The boundary-element method (BEM) is applied to calculate target strength (TS) and extinction cross-section of a scatterer. The scattering amplitudes of four types of prolate spheroid, namely, the vacant, rigid, liquid-filled, and gas-filled, are calculated using the BEM. Comparison between the results of the BEM and the prolate-spheroid model (PSM), which is a numerical calculation using spheroidal-wave functions, shows excellent agreement for the vacant, rigid, and liquid-filled spheroids. The TS of a gas-filled prolate spheroid, calculated by the BEM, shows resonance at a low frequency. The lowest resonant frequency, the peak ratio, and the quality factor (Q) of this resonance are compared with those given by the T-matrix and an analytical solution. Again the results show excellent agreement.