bluuebunny/crossref_metadata_2025 huggingface dataset:
A Functionally Graded Plane With a Circular Inclusion Under Uniform Antiplane Eigenstrain
Authors: Wang X. , Pan E. , Roy A. K.
Published: April 2008

The problem of a functionally graded plane with a circular inclusion under a uniform antiplane eigenstrain is investigated, where the shear modulus varies exponentially along the x direction. By introducing a new function which satisfies the Helmholtz equation, the general solution to the original problem is derived in terms of series expansion. Numerical results are then presented which demonstrate clearly that for a functionally graded plane, the strain and stress fields inside the circular inclusion under uniform antiplane eigenstrains are intrinsically nonuniform. This phenomenon differs from the corresponding homogeneous material case where both the strain and stress fields are uniform inside the circular inclusion.
Solution for a Semi-Permeable Interface Crack in Elastic Dielectric/Piezoelectric Bimaterials
Authors: Li Q. , Chen Y. H.
Published: April 2008

A semi-permeable interface crack in infinite elastic dielectric/piezoelectric bimaterials under combined electric and mechanical loading is studied by using the Stroh complex variable theory. Attention is focused on the influence induced from the permittivity of the medium inside the crack gap on the near-tip singularity and on the energy release rate (ERR). Thirty five kinds of such bimaterials are considered, which are constructed by five kinds of elastic dielectrics and seven kinds of piezoelectrics, respectively. Numerical results for the interface crack tip singularities are calculated. We demonstrate that, whatever the dielectric phase is much softer or much harder than the piezoelectric phase, the structure of the singular field near the semi-permeable interface crack tip in such bimaterials always consists of the singularity r−1∕2 and a pair of oscillatory singularities r−1∕2±iε. Calculated values of the oscillatory index ε for the 35 kinds of bimaterials are presented in tables, which are always within the range between 0.046 and 0.088. Energy analyses for five kinds of such bimaterials constructed by PZT-4 and the five kinds of elastic dielectrics are studied in more detail under four different cases: (i) the crack is electrically conducting, (ii) the crack gap is filled with air/vacuum, (iii) the crack gap is filled with silicon oil, and (iv) the crack is electrically impermeable. Detailed comparisons on the variable tendencies of the crack tip ERR against the applied electric field are given under some practical electromechanical loading levels. We conclude that the different values of the permittivity have no influence on the crack tip singularity but have significant influences on the crack tip ERR. We also conclude that the previous investigations under the impermeable crack model are incorrect since the results of the ERR for the impermeable crack show significant discrepancies from those for the semi-permeable crack, whereas the previous investigations under the conducting crack model may be accepted in a tolerant way since the results of the ERR show very small discrepancies from those for the semi-permeable crack, especially when the crack gap is filled with silicon oil. In all cases under consideration the curves of the ERR for silicon oil are more likely tending to those for the conducting crack rather than to those for air or vacuum. Finally, we conclude that the variable tendencies of the ERR against the applied electric field have an interesting load-dependent feature when the applied mechanical loading increases. This feature is due to the nonlinear relation between the normal electric displacement component and the applied electromechanical loadings from a quadratic equation.
Passive Control of Limit Cycle Oscillations in a Thermoacoustic System Using Asymmetry
Authors: Eisenhower Bryan , Hagen Gregory , Banaszuk Andrzej , Mezić Igor
Published: April 2008

In this paper we investigate oscillations of a dynamical system containing passive dynamics driven by a positive feedback and how spatial characteristics (i.e., symmetry) affect the amplitude and stability of its nominal limit cycling response. The physical motivation of this problem is thermoacoustic dynamics in a gas turbine combustor. The spatial domain is periodic (passive annular acoustics) which are driven by heat released from a combustion process, and with sufficient driving through this nonlinear feedback a limit cycle is produced which is exhibited by a traveling acoustic wave around this annulus. We show that this response can be controlled passively by spatial perturbation in the symmetry of acoustic parameters. We find the critical parameter values that affect this oscillation, study the bifurcation properties, and subsequently use harmonic balance and temporal averaging to characterize periodic solutions and their stability. In all of these cases, we carry a parameter associated with the spatial symmetry of the acoustics and investigate how this symmetry affects the system response. The contribution of this paper is a unique analysis of a particular physical phenomena, as well as illustrating the equivalence of different nonlinear analysis tools for this analysis.
A Point Heat Source on the Surface of a Semi-Infinite Transversely Isotropic Piezothermoelastic Material
Authors: Hou Peng-Fei , Luo Wei , Leung Andrew Y. T.
Published: April 2008

We use the compact harmonic general solutions of transversely isotropic piezothermoelastic materials to construct the three-dimensional Green’s function of a steady point heat source on the surface of a semi-infinite transversely isotropic piezothermoelastic material by four newly introduced harmonic functions. All components of the coupled field are expressed in terms of elementary functions and are convenient to use. Numerical results for cadmium selenide are given graphically by contours.
Free Convection and Mass Transfer Flow Near a Moving Vertical Porous Plate: An Analytical Solution
Authors: Toki C. J.
Published: April 2008

An exact solution of the problem of the unsteady free convection and mass transfer flow near an infinite vertical porous plate, which moves with time-dependent velocity in a viscous and incompressible fluid, is presented here by the Laplace transform technique. All expressions of the new solutions of the present problem were obtained in closed forms with arbitrary Prandtl number (Pr), Schmidt number (Sc), thermal Grashof number (Gr), and mass Grashof number (Gm). Two applications of physical interest for porous or nonporous plate are discussed. Applying numerical values into the expressions of analytical solution, we was also discussed the vertical air flows—the usual phenomenon at plumes into the atmosphere.
Boundary Perturbation Solution for Nearly Circular Holes and Rigid Inclusions in an Infinite Elastic Medium
Authors: Ekneligoda Thushan C. , Zimmerman Robert W.
Published: April 2008

The boundary perturbation method is used to solve the problem of a nearly circular rigid inclusion in a two-dimensional elastic medium subjected to hydrostatic stress at infinity. The solution is taken to the fourth order in the small parameter epsilon that quantifies the magnitude of the variation of the radius of the inclusion. This result is then used to find the effective bulk modulus of a body that contains a dilute concentration of such inclusions. The corresponding results for a cavity are obtained by setting the Muskhelishvili coefficient κ equal to −1, as specified by the Dundurs correspondence principle. The results for nearly circular pores can be expressed in terms of the pore compressibility. The pore compressibilities given by the perturbation solution are tested against numerical values obtained using the boundary element method, and are shown to have good accuracy over a substantial range of roughness values.
Analysis of Unsteady Flow Through a Microtube With Wall Slip and Given Inlet Volume Flow Rate Variations
Authors: Chen Chun-I , Chen Cha’o-Kuang , Lin Heng-Ju
Published: April 2008

This study examines the effects of rarefaction of an unsteady flow through a microtube for a given but arbitrary inlet volume flow rate. Four cases of inlet volume flow rate proposed by Das and Arakeri (2000, ASME J. Appl. Mech., 67, pp. 274–281) are as follows: (1) trapezoidal piston motion, (2) constant acceleration, (3) impulsively started flow, and (4) impulsively blocked fully developed flow. During the analysis process, the Knudsen number (Kn) is used to represent the degree of rarefaction. The analytical results are presented graphically and compared to the results for a continuum under a no-slip condition. The effect of wall-slip became significant with the increasing degrees of rarefaction. The velocity in the boundary layer increased, whereas the velocity in the potential core of the microtube decreased, under the same condition. The influence of the rarefaction for the pressure gradient varied for the four cases.
Dynamic Response Characteristics of a Nonviscously Damped Oscillator
Authors: Adhikari S.
Published: April 2008

The characteristics of the frequency response function of a nonviscously damped linear oscillator are considered in this paper. It is assumed that the nonviscous damping force depends on the past history of velocity via a convolution integral over an exponentially decaying kernel function. The classical dynamic response properties, known for viscously damped oscillators, have been generalized to such nonviscously damped oscillators. The following questions of fundamental interest have been addressed: (a) Under what conditions can the amplitude of the frequency response function reach a maximum value?, (b) At what frequency will it occur?, and (c) What will be the value of the maximum amplitude of the frequency response function? Introducing two nondimensional factors, namely, the viscous damping factor and the nonviscous damping factor, we have provided exact answers to these questions. Wherever possible, attempts have been made to relate the new results with equivalent classical results for a viscously damped oscillator. It is shown that the classical concepts based on viscously damped systems can be extended to a nonviscously damped system only under certain conditions.
A Time-Varying Stiffness Rotor Active Magnetic Bearings Under Combined Resonance
Authors: Hegazy U. H. , Eissa M. H. , Amer Y. A.
Published: April 2008

This paper is concerned with the nonlinear oscillations and dynamic behavior of a rigid disk-rotor supported by active magnetic bearings (AMB), without gyroscopic effects. The nonlinear equations of motion are derived considering a periodically time-varying stiffness. The method of multiple scales is applied to obtain four first-order differential equations that describe the modulation of the amplitudes and the phases of the vibrations in the horizontal and vertical directions. The stability and the steady-state response of the system at a combination resonance for various parameters are studied numerically, applying the frequency response function method. It is shown that the system exhibits many typical nonlinear behaviors, including multiple-valued solutions, jump phenomenon, hardening, and softening nonlinearity. A numerical simulation using a fourth-order Runge-Kutta algorithm is carried out, where different effects of the system parameters on the nonlinear response of the rotor are reported and compared to the results from the multiple scale analysis. Results are compared to available published work.
Wave Propagation Analysis in Anisotropic Plate Using Wavelet Spectral Element Approach
Authors: Mitra Mira , Gopalakrishnan S.
Published: April 2008

In this paper, a 2D wavelet-based spectral finite element (WSFE) is developed for a anisotropic laminated composite plate to study wave propagation. Spectral element model captures the exact inertial distribution as the governing partial differential equations (PDEs) are solved exactly in the transformed frequency-wave-number domain. Thus, the method results in large computational savings compared to conventional finite element (FE) modeling, particularly for wave propagation analysis. In this approach, first, Daubechies scaling function approximation is used in both time and one spatial dimensions to reduce the coupled PDEs to a set of ordinary differential equations (ODEs). Similar to the conventional fast Fourier transform (FFT) based spectral finite element (FSFE), the frequency-dependent wave characteristics can also be extracted directly from the present formulation. However, most importantly, the use of localized basis functions in the present 2D WSFE method circumvents several limitations of the corresponding 2D FSFE technique. Here, the formulated element is used to study wave propagation in laminated composite plates with different ply orientations, both in time and frequency domains.
A Reciprocity Relation Couples Newtonian and Eshelbian Mechanics
Authors: Herrmann G. , Kienzler R.
Published: April 2008

By considering a stressed elastic body subjected sequentially to a material displacement of a defect and the application of a physical force, the authors have succeeded in arriving at a novel type of coupling of Newtonian and Eshelbian mechanics by means of a reciprocity theorem analogous to that of Maxwell. This reciprocity relation is more involved than those in strictly physical or strictly material space. An order of magnitude analysis was required to obtain consistent relations. Several illustrative examples are worked out, and suggestions for some experiments, which in their evaluations would make use of the new expressions, are offered.
Responses of growth, morphology, and anatomy to salinity and calcium supply in cultivated and wild barley
Authors: Huang J. , Redmann R. E.
Published: April 2008

Growth, morphology, and anatomy were examined in cultivated barley (Hordeum vulgare L. cv. Harrington), and wild barley (Hordeum jubatum L.) collected from a wild population located in Saskatoon, Sask. Plants were grown in nutrient solution plus mixed sulphate salts with low or high calcium supply and in nutrient solution alone (control), using a hydroponic system in a growth chamber. Salt stress had greater deleterious effects on growth, morphology, and anatomy of 'Harrington' than wild barley. Additional Ca supply markedly improved these parameters in 'Harrington' but not in wild barley, suggesting a greater responsiveness to Ca in the cultivated species. The wild barley population had greater leaf and tiller numbers per plant but smaller leaf area and dry mass than 'Harrington' in control solution. After 20 days of salt treatment, 'Harrington' showed a greater reduction in tiller and leaf number, shoot height and root length, and tissue dry mass than wild barley. Calcium-deficiency symptoms were found in 'Harrington' leaves in the low Ca salt treatment but not in wild barley. On the other hand, shoot height and dry mass growth were significantly increased in 'Harrington' by high Ca salt treatment, suggesting that 'Harrington' was more responsive to supplemental Ca than wild barley. Salt stress induced thicker roots with larger vessels in 'Harrington' but not in the wild barley population. Key words: calcium nutrition, Hordeum vulgare L., Hordeum jubatum L., hydraulic resistance, salt tolerance, root anatomy, sulphate salinity.
Formation et distribution de glace dans les bourgeons de Vitis vinifera avant et au cours de leur débourrement
Authors: Barka E. Aït , Audran J. C. , Brun O. , Leddet C. , Dereuddre J.
Published: April 2008

Evolution of the exothermic profile of latent buds of Vitis vinifera L. cv. Pinot noir was followed using differential scanning microcalorimetry. Analyses performed on buds at the winterized state (stage 1), on wolly buds (stage 3), and on green pointing buds (stage 5) showed that modes and speed of extracellular and intracellular liquid crystallisation vary according to the phenological stage and are closely linked to the meristematic tissues. Among these, the vascular system plays a major role in the crystallisation process. Indeed, within the winterized buds, where it is at the procambial stage, i.e. nonfunctional, it forms a barrier to the propagation of ice toward the apical part of the bud where water remains in a prolongated surfusion state. On the opposite, during the period preceeding bud opening, from stage 3 to stage 5, where its differentiation leads to a continuous and functional vascular system connecting the bud base to its apical part, it forms a preferred path allowing rapid ice propagation, leading to a violent ice setting in all the tissues. Key words: latent bud, exotherm, calorimetry, vascular system, wine. [Journal translation]
The genus Fimetariella
Authors: Krug John C.
Published: April 2008

The taxonomy and phylogenetic relationships of the fungal genus Fimetariella (Ascomycotina, Lasiosphaeriaceae) are discussed. A revised generic description and key are presented. Descriptions and illustrations are provided for all taxa. Fimetariella dunarum n.comb. and Fimetariella apotoma, Fimetariella brachycaulina, Fimetariella dolichopoda, Fimetariella macromischa, Fimetariella microsperma, and Fimetariella tetraspora n.spp. are proposed. A phialidic anamorph resembling Cladorrhinum is reported for F. microsperma. The ascospores of the type species Fimetariella rabenhorstii are considered to possess two terminal germ pores, one large pore and one very small pore, along with several small, apparently nonfunctional pores. A key to the genera with these minor pores is included. Key words: Fimetariella, Cladorrhinum, coprophilous, fungi, keys, taxonomy.
Reproduction of Viola mirabilis in relation to light and nutrient availability
Authors: Mattila Tanja , Salonen Veikko
Published: April 2008

Mixed mating strategies in plants, such as chasmogamy and cleistogamy, may have evolved to optimize reproductive response to local, often variable, environmental conditions. A 2-year field experiment was conducted to examine the effects of light and nutrient availability on growth and chasmogamous and cleistogamous flower and fruit production in Viola mirabilis, a perennial forest understory herb. Using a factorial design, we examined whether the mode of reproduction or reproductive output of V. mirabilis would be influenced by a repeated fertilizer application and (or) gradual shading with artificial plants. In this population of V. mirabilis, the predominant mode of reproduction during both study years was chasmogamy. In the 2nd year of study, the number of both chasmogamous and cleistogamous flowers per plant decreased with decreasing light intensity, while the increased nutrient supply had no effect on flower or fruit production or plant growth. In addition, the proportion of cleistogamous flowers was smaller for shaded plants. However, the change in the proportion of cleistogamous or chasmogamous flowers from 1993 to 1994 was not affected by shading or fertilization. The production of cleistogamous flowers correlated positively with final total leaf area during both study years, while no correlation was found between the number of chasmogamous flowers and leaf area. In most studies, chasmogamy has been found to be dependent on plant size and favourable environmental conditions, whereas cleistogamy is generally considered to be relatively independent of these factors. However, our results suggest that only plants reaching a large size were capable of producing cleistogamous flowers in addition to chasmogamous flowers produced earlier in the season. Also, it seems that the general assumption of cleistogamic reproduction as a more advantageous mode of reproduction in poor light conditions compared with chasmogamy does not apply to V. mirabilis. Key words: chasmogamy, cleistogamy, light, nutrients, reproductive success, Viola mirabilis.
Indigenous and introduced populations ofAgaricus bisporus, the cultivated button mushroom, in eastern and western Canada: implications for population biology, resource management, and conservation of genetic diversity
Authors: Kerrigan Richard W. , Carvalho Daisy B. , Horgen Paul A. , Anderson James B.
Published: April 2008

Agaricus bisporus is known from field collections in several parts of southern Canada and the border states of Washington and Idaho. In Ontario, the species is associated with urban horticultural sites, agricultural areas, and thoroughfares. In British Columbia, Washington, and Idaho, the species is less well documented but occurs in habitats similar to those in Ontario. All studied isolates from these two regions were genotypically similar to those collected in Europe and also to a representative sample of cultivar isolates believed to be of European origin. In contrast, a population from forests of Picea in the Rocky Mountains of Alberta had genotypes that are very different from European and cultivar groups, including the putatively introduced populations in other parts of Canada. To a lesser extent, the Albertan individuals also differed from three other isolated natural populations, two in California and one in Israel. Two of 35 isolates from Alberta had nuclear genotypes that were partially or entirely consistent with European ancestry, indicating that foreign (probably cultivar) germ plasm has become established in the native habitat. Thirty of 35 isolates from the Alberta field sample had one of six mitochondrial DNA (mtDNA) haplotypes known only from Alberta; the remaining five had an mtDNA type known from cultivar strains. However, nuclear genotypic similarity to other Albertan or European-cultivar isolates was not significantly correlated with presence or absence of this latter mtDNA type. The genetic diversity represented by the previously unknown Albertan population, and to a lesser extent by the heirloom varietal lineages and their derivatives that have become established in Ontario, British Columbia, Washington, and Idaho, is an important resource for breeders of this valuable fungal crop species. Threats to resource populations of this species, and possible responses, are discussed. Key words: Agaricus bisporus, mushroom population biology, resource management, germ plasm conservation, genetic diversity, microphylogeny.
Flavonoid chemistry of Calyceraceae
Authors: Bohm Bruce A. , Reid Alan , DeVore Melanie , Stuessy Tod F.
Published: April 2008

Flavonoid profiles were determined for 11 species representing five genera of Calyceraceae: Acicarpha, Boöpis, Calycera, Gamocarpha, and Nastanthus. Kaempferol, quercetin, 6-methoxykaempferol, and 6-methoxyquercetin (patuletin) were unequivocally identified. Kaempferol and quercetin occurred as 3-O-mono- and 3-O-diglycosides, whereas the latter two flavonols were observed only as aglycones. Several unidentified phenolic compounds were also noted. The simplest profile in the family consisted solely of the kaempferol and quercetin glycosides in Acicarpha, Gamocarpha, and one specimen of Calycera leucanthema. Morphological evidence suggests that Acicarpha represents prototypical Calyceraceae and that a close relationship exists between primitive Calyceraceae and some basal members of Asteraceae (subfamily Barnadesioideae). This last possibility is reinforced by the similarity of flavonoid profiles of Acicarpha and members of Barnadesioideae. Key words: Calyceraceae, Asteraceae, Compositae, Barnadesioideae, flavonoids.
Rod-shaped virus-like particles in the endoplasmic reticulum ofAudouinella saviana(Acrochaetiales, Rhodophyta)
Authors: Pueschel Curt M.
Published: April 2008

Rod-shaped particles, approximately 30 nm in width and 1000 nm or more in length, were found in cells of the red alga Audouinella saviana (Meneghini) Woelkerling. Parallel in orientation and hexagonally packed, these inclusions were located within dilated cisternae of rough endoplasmic reticulum. The rods consisted of an electron-dense central element surrounded by a thick-walled tube that appeared to be composed of repeating granular subunits. Although uninfected controls of the same species were not available, the morphology and substructure of the inclusions, the absence of such inclusions in other species of Audouinella, and the apparent connection of these particles with cellular abnormalities and necrosis suggest that these inclusions may be viral in nature. Among the unusual and possibly cytopathic features of cells containing particles were ropy, fibrillar structures free in the cytoplasm, corrugated mitochondrial cristae, amorphous mitochondrial inclusions, highly convoluted photosynthetic membranes, and loss of integrity of the nuclear envelope. This is the first report of the presence of possible rod-shaped virus-like particles in red algae. Key words: Acrochaetiales, Audouinella saviana, Rhodophyta, ultrastructure, virus-like particles.
The hybrid nature of Lycium ciliatum × cestroides (Solanaceae): experimental, anatomical, and cytological evidence
Authors: Bernardello Luis , Rodriguez Ivana , Stiefkens Laura , Galetto Leonardo
Published: April 2008

The hybrid nature of Lycium ciliatum × cestroides Hieron. is supported through experimental crosses. Using L. ciliatum Schlecht. as a female parent, 57% of crosses set fruit with hybrid seeds, whereas reciprocal crosses were unsuccessful. Seeds had a high germination rate (76%). F1 plants obtained agree with the herbarium specimens previously cited as putative hybrid and with a living plant we found in Córdoba (Argentina). Leaf, stem, and flower anatomy, karyotype composition, and chemical nectar composition were analyzed in the artificial and the natural hybrid. Results were compared with similar data on the parental species. Most of the studied features were intermediate between those of the parental species, as supported by principal component analysis. The origin of this hybrid may be due to pollen transfer mediated by bumblebees that occasionally visit both parental species. The distribution of the parental species overlaps in a wide Chaco region showing no spatial, environmental, or external reproductive isolating mechanisms. Results indicate there is a hybrid breakdown in the progeny of the hybrid that would restrict the natural interspecific gene flow. Key words: Lycium ciliatum × cestroides, hybrid, karyotype, anatomy, crosses, flower visitors.
Release pattern for potassium from decomposing forest needle and leaf litter. Long-term decomposition in a Scots pine forest. IX.
Authors: Laskowski Ryszard , Berg Björn , Johansson Maj-Britt , McClaugherty Charles
Published: April 2008

A general pattern for the dynamics of K in decomposing leaf and needle litters is described, based on 139 litter decomposition studies carried out in forests of northern and central Europe and the northern United States. We distinguished an initial phase of fast changes in K concentration and a later one in which the litter was close to humus and all K appeared to be immobile. In the initial phase the rate of change in K concentration was related to the initial K concentration: the higher the initial concentration, the faster its decrease and the faster the quantitative release of K. For litters with particularly low initial K concentrations, an increase in concentration was observed from the very start of decomposition. In the late phase a slight increase in concentrations was observed. After ca. 60% accumulated mass loss, K concentrations approached similar levels in various litter types, irrespective of the litter type and initial concentrations. We also estimated a theoretical equilibrium state at which no change in K concentration should be expected. According to our estimates these equilibrium concentrations ranged from approx. 0.8 mg/g dry mass of litter for Scots pine to approx. 1.2 mg/g dry mass for deciduous litter types. The estimate of K concentration in Scots pine litter in late decomposition stages was very close to that measured in the humus at the same site. Based on the wide variety of litter types and sites studied we conclude that the pattern suggested for K dynamics in decomposing litter holds at least for European coniferous forests north of the Alps and the Carpathians. Key words: potassium, dynamics, release, litter, humus, decomposition.
Novel bisindolylmaleimide derivative inhibits mitochondrial permeability transition pore and protects the heart from reperfusion injury
Authors: Katare Rajesh Gopalrao , Zhitian Zou , Sodeoka Mikiko , Sasaguri Shiro
Published: April 2008

Despite major advances in treating patients with coronary heart disease, reperfusion injury is still considered to be a major problem, especially in surgical settings. Here, we demonstrate the protective effects of a novel bisindolylmaleimide derivative, MS1 (2-[1-(3-aminopropyl)indol-3-yl]-3-(indol-3-yl)-N-methylmaleimide), against reperfusion injury of the heart. After anesthesia and artificial ventilation, Wistar rats were subjected to 30 min of left coronary artery occlusion followed by 120 min of reperfusion with or without treating the rats with MS1 (2.25 μmol·L–1·kg–1) before left coronary artery occlusion. Compared with the untreated hearts, MS1 treatment significantly reduced myocardial infarct size (35.1% ± 3% vs. 75.5% ± 5%, p < 0.001), reduced prevalence of apoptotic cells (2.6% ± 0.5% vs. 12.2% ± 2.1%, p < 0.001), prevented mitochondrial swelling and cytochrome c release, inhibited downregulation of antiapoptotic protein Bcl-2 expression, and suppressed caspase-3 activation. In contrast, pretreatment with atractyloside, a mitochondrial permeability transition pore opener, abolished the protective effects of MS1. In conclusion, MS1 inhibits pathologic opening of permeability transition pores and protects the heart against reperfusion injury and pathologic apoptosis.
Oxidative stress in primary culture hepatocytes isolated from partially hepatectomized rats
Authors: Francés Daniel , Ronco M. Teresa , Ochoa Elena , Alvarez M. Luján , Quiroga Ariel , Parody J. Pablo , Monti Juan , Carrillo M. Cristina , Carnovale Cristina E.
Published: April 2008

The aim of this study was to evaluate the influence of partial hepatectomy prior to cell isolation on hepatocytes in vitro. We characterized the possible changes of various stress oxidative parameters within the first 24 h after seeding. Male Wistar rats served as donors. Hepatocytes were isolated by collagenase digestion from either liver of simulated surgery (SH) or from liver 1 h after 70% hepatectomy (PH), and the changes in stress parameters were analyzed after 1, 3, 18, and 24 h in culture. At 24 h, only hepatocytes from PH maintained significantly increased reactive oxygen species production, oxidized glutathione percentage, and Cu/Zn superoxide dismutase and catalase activities. Our results show that hepatocytes suffer significant cell injury as a result of the isolation procedure, but primary cultured cells from SH metabolically recover from this stress after 18 h. After this time, primary culture hepatocytes primed by PH maintain their in vivo-like metabolic activities (increase in both oxidative stress and antioxidant status).
Older versus newer antidepressants: Substance P or calcium antagonism?
Authors: Boselli C. , Barbone M. Santagostino , Lucchelli A.
Published: April 2008

Substance P (SP) is possibly involved in the pathophysiology of depression and anxiety. We investigated interactions between antidepressants on SP-induced effects and their potential calcium-blocking activity in the isolated guinea pig ileum. All the antidepressants tested, except pargyline, moclobemide, mianserin, and reboxetine, were able to inhibit in a concentration-dependent manner the contraction induced by 100 nmol/L SP. Clomipramine, fluoxetine, maprotiline, and amitriptyline (all at 3 μmol/L) flattened the concentration–response curves to SP, resulting in a reduction of up to 59%, 63%, 32%, and 23%, respectively, of the maximum contractile effect. All the antidepressants tested (3 μmol/L), except pargyline, moclobemide, and mianserin, produced a rightward parallel shift of the concentration–response curve to CaCl2. The L-type selective calcium blocker nifedipine and the T-type selective mibefradil showed similar behaviour against both agonists used, SP and CaCl2. The relative order of potency was nifedipine (pA2, 7.6 ± 0.1) > clomipramine (pA2, 7.0 ± 0.1) > fluoxetine (pKB, 6.5 ± 0.1) = mibefradil (pKB, 6.6 ± 0.1) > amitriptyline (pKB, 6.3 ± 0.1) = maprotiline (pKB, 6.2 ± 0.1) > fluvoxamine (pKB, 5.9 ± 0.1). The data reported in the present study suggest that the antidepressants tested did not behave as competitive antagonists versus NK1-receptor subtypes, but their inhibitory action seems to be related to their calcium-blocking properties.
Inhibitory effects of aqueous extract of Hibiscus sabdariffa on contractility of the rat bladder and uterus
Authors: Fouda Abdel-Motaal M. , Daba Mohamad-Hesham Y. , Dahab Gamal M.
Published: April 2008

We examined an aqueous extract of Hibiscus sabdariffa calyces extracts (HSE) by close-arterial injection on micturition thresholds (MTs) and on uterine contractions (rate and amplitude). Five doses of HSE were examined (1, 5, 10, 50, and 100 mg/kg) in 3 groups of rats: controls, after bladder inflammation, and after bilateral hypogastric neurectomy. In some rats, uterine contractions were induced by injection of oxytocin (OT) and the effect of HSE was compared with that of nifedipine. HSE increased MTs in a dose-dependent manner in all groups. Neither atropine (0.1 mg/kg) nor propranolol (0.4 mg/kg) had significant effects on cystometric parameters. They also did not affect the responses obtained by HSE on cystometric parameters. As with bladder response, HSE inhibited both the rate and amplitude of uterine contractions in all groups in a dose-dependent manner. The uterine response to HSE was not affected by administration of either atropine or propranolol. A slight, but significant, reduction of contraction amplitude by HSE in the OT precontracted uteri was only noted at a dose of 500 mg/kg. Nifedipine was more potent than HSE in reducing uterine contraction amplitude. The present work documents inhibition by HSE of the rat bladder and uterine contractility in a dose-dependent manner via a mechanism unrelated to local or remote autonomic receptors or calcium channels. However, further investigation is needed to establish the exact mechanism of action.
Moderate body hypothermia alleviates behavioral and EEG manifestations of audiogenic seizures in metaphit-treated rats
Authors: Hrnčić Dragan , Vučević Danijela , Rašić Aleksandra , Radosavljević Tatjana , Mladenović Dušan , Šušić Veselinka , Djurić Dragan , Stanojlović Olivera
Published: April 2008

We investigated the effects of hypothermia on the incidence and EEG signs of audiogenic seizures in rats treated with metaphit (1-[1(3isothiocyanatophenyl)-cyclohexyl] piperidine), an experimental model of generalized reflex epilepsy. After i.p. injection with metaphit (10 mg/kg) Wistar rats were exposed to audiogenic stimulation at hourly intervals during the time course of the experiment. After intermittent use of an ice pack 8 h after the metaphit treatment, when seizure was fully developed, the body temperature was reduced to 30 ± 0.5 °C in one half of the rats, and maintained at 37 ± 0.5 °C in the other half. Saline-injected rats served as a control group. In the hypothermia group, the incidence of audiogenic seizures induced by metaphit was completely suppressed during the 3 consecutive testing times, while no signs of epileptiform activity were noted in EEG tracings. The termination of hypothermic treatment resulted in the recovery of seizure susceptibility, and during audiogenic stimulation, bursts of spiking activity were recorded in the EEGs of metaphit-treated rats. These findings indicate that moderate body hypothermia is an effective anticonvulsant treatment for audiogenic seizures in metaphit-treated rats.
Effect of chronic lithium administration on endothelium-dependent relaxation of rat mesenteric bed: role of nitric oxide
Authors: Afsharimani Banafsheh , Moezi Leila , Sadeghipour Hamed , Rahimzadeh-Rofouyi Bahareh , Nobakht Maliheh , Sanatkar Mehdi , Ghahremani Mohammad Hosein , Dehpour Ahmad R.
Published: April 2008

The mechanism of action of lithium, an effective treatment for bipolar disease, is still unknown. In this study, the mesenteric vascular beds of control rats and rats that were chronically treated with lithium were prepared by the McGregor method, and the mesenteric vascular bed vasorelaxation responses were examined. NADPH-diaphorase histochemistry was used to determine the activity of NOS (nitric oxide synthase) in mesenteric vascular beds. We demonstrated that ACh-induced vasorelaxation increased in the mesenteric vascular bed of rats treated with lithium. Acute Nο-nitro-l-arginine methyl ester (l-NAME) administration in the medium blocked ACh-induced vasorelaxation in the control group more effectively than in lithium-treated rats, while the vasorelaxant response to sodium nitroprusside, a NO donor, was not different between lithium-treated and control groups. Acute aminoguanidine administration blocked ACh-induced vasorelaxation of lithium-treated rats, but had no effect in the control rats. Furthermore, NOS activity, determined by NADPH-diaphorase staining, was significantly greater in the mesenteric vascular beds from chronic lithium-treated rats than in those from control rats. These data suggest that the enhanced ACh-induced endothelium-derived vasorelaxation in rat mesenteric bed from chronic lithium-treated rats might be associated with increased NOS activity, likely via iNOS. Simultaneous acute l-NAME and indomethacin administration suggests the possible upregulation of EDHF (endothelium-derived hyperpolarizing factor) in lithium-treated rats.
Both enalapril and losartan attenuate sarcolemmal Na+-K+-ATPase remodeling in failing rat heart due to myocardial infarctionThis article is one of a selection of papers published in the special issue Bridging the Gap: Where Progress in Cardiovascular and Neurophysiologic Research Meet.
Authors: Guo Xiaobing , Wang Jingwei , Elimban Vijayan , Dhalla Naranjan S.
Published: April 2008

To investigate the mechanisms underlying the depressed sarcolemmal (SL) Na+-K+-ATPase activity in congestive heart failure (CHF), different isoforms and gene expression of Na+-K+-ATPase were examined in the failing left ventricle (LV) at 8 weeks after myocardial infarction (MI). In view of the increased activity of renin–angiotensin system (RAS) in CHF, these parameters were also studied after 5 weeks of treatment with enalapril (10 mg·kg–1·day–1), an angiotensin-converting enzyme inhibitor, and losartan (20 mg·kg–1·day–1), an angiotensin II type 1 receptor antagonist, starting at 3 weeks after the coronary ligation in rats. The infarcted animals showed LV dysfunction and depressed SL Na+-K+-ATPase activity. Protein content and mRNA levels for Na+-K+-ATPase α2isoform were decreased whereas those for Na+-K+-ATPase α3isoform were increased in the failing LV. On the other hand, no significant changes were observed in protein content or mRNA levels for Na+-K+-ATPase α1and β1isoforms. The treatment of infarcted animals with enalapril or losartan improved LV function and attenuated the depression in Na+-K+-ATPase α2isoform as well as the increase in α3isoform, at both the protein and mRNA levels; however, combination therapy with enalapril and losartan did not produce any additive effects. These results provide further evidence that CHF due to MI is associated with remodeling of SL membrane and suggest that the blockade of RAS plays an important role in preventing these alterations in the failing heart.
Correlation between electrocorticographic and motor phenomena in lindane-induced experimental epilepsy in ratsThis article is one of a selection of papers published in the special issue Bridging the Gap: Where Progress in Cardiovascular and Neurophysiologic Research Meet.
Authors: Vučević Danijela , Hrnčić Dragan , Radosavljević Tatjana , Mladenović Dušan , Rašić-Marković Aleksandra , Lončar-Stevanović Helena , Djurić Dragan , Macut Djuro , Šušić Veselinka , Stanojlović Olivera
Published: April 2008

We report a study on the relation between open-field behavior and electroencephalographic (EEG) changes during lindane-induced seizures in 2-month-old adult male Wistar rats. For chronic EEG recordings and power spectra analysis, 3 electrodes were implanted into the skull. Three groups of animals, (i) saline-injected control (n = 6), (ii) DMSO-treated (n = 6), and (iii) lindane intraperitoneally administered: L4 (4 mg/kg, n = 10), L6 (6 mg/kg, n = 11), and L8 (8 mg/kg, n = 11), were observed for 30 min for the occurrence of convulsive behavior. It was assessed by incidence of motor seizures, and seizure severity grade was determined by a descriptive rating scale (0, no response; 1, head nodding, lower jaw twitching; 2, myoclonic body jerks, bilateral forelimb clonus with full rearing; 3, progression to generalized clonic convulsions followed by tonic extension of fore and hind limbs and tail; 4, status epilepticus). EEG signal and spectral analyses were suitable to describe the dynamics of complex behavioral responses. Incidence and severity of epileptic manifestations, recorded as high voltage spike-wave complexes, polyspikes, sleep-like patterns in EEG, and power spectra changes, were greater in lindane-treated groups in a dose-dependent manner compared with control or DMSO-treated groups. Our results suggest good correlation between lindane-induced epileptiform activity and behavioral changes.
Inflammatory cytokines and malnutrition as related to risk for cardiovascular disease in hemodialysis patientsThis article is one of a selection of papers published in the special issue Bridging the Gap: Where Progress in Cardiovascular and Neurophysiologic Research Meet.
Authors: Perunicic-Pekovic G. , Pljesa S. , Rasic-Milutinovic Z. , Stankovic S. , Ilic M. , Maletic R.
Published: April 2008

Malnutrition and inflammation are associated with end-stage renal disease (ESRD). Interleukin (IL)-6 and tumor necrosis factor alpha (TNF-α) powerfully predict death from cardiovascular disease. The aim of our study was to establish an association between markers of inflammation and parameters of malnutrition in patients on hemodialysis. The study population consisted of 42 hemodialysis patients with different parameters of malnutrition. Blood samples were taken after an overnight fast, and plasma lipid profiles (total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides) were measured by using conventional enzymatic methods. Serum urea and creatinine levels were also measured by routine procedures. Plasma high-sensitivity C-reactive protein level (hs-CRP), TNF-α, and IL-6 were measured by enzyme-linked immunosorbent assay (ELISA). Standard Doppler echo examinations were used to determine plaque on carotid arteries, and end-diastolic diameter (EDD) and ejection fraction (EF) were measured by echocardiography. Malnourished patients exhibited significantly greater evidence of cardiovascular disease and carotid plaques. Factor (principal component) analysis indicated 6 latent factors with 67.5% of the variance explained within all investigated parameters. Cluster analysis was used to distinguish the inflammatory markers and the nutritional markers from other parameters and to visualize similarities between variables. In summary, this cross-sectional study in hemodialysis patients found a high prevalence of malnutrition, inflammation, carotid plaques, and cardiovascular disease. Malnourished dialysis patients are more often found with cardiovascular disease and carotid plaques. In addition, these patients have higher levels of inflammatory cytokines, which may partly explain the elevated risk for atherosclerotic vascular disease.
Effects of long-term losartan andl-arginine treatment on haemodynamics, glomerular filtration, and SOD activity in spontaneously hypertensive ratsThis article is one of a selection of papers published in the special issue Bridging the Gap: Where Progress in Cardiovascular and Neurophysiologic Research Meet.
Authors: Miloradović Zoran , Jovović Đurđica , Mihailović-Stanojević Nevena , Milanović Jelica Grujić , Milanović Slađan
Published: April 2008

Recently, it has been reported that losartan, an angiotensin II receptor (ATR) antagonist, depresses the angiotensin II-induced production of superoxide radicals. Also, in spontaneously hypertensive rats (SHR) endothelial dysfunction is associated with decreased nitric oxide (NO) synthesis. In this study, we examined the effects of long-term ATR blockade and l-arginine supplementation on the haemodynamic parameters, glomerular filtration, and oxidative status in SHR. Adult male SHR were treated with losartan (10 mg/kg) and with the NO donor l-arginine (2 g/kg) for 4 weeks. The animals were divided into the following experimental groups: control (n = 7), l-arginine (n = 7), losartan (n = 7), and l-arginine + losartan (n = 7). Mean arterial pressure (MAP), regional blood flow, urea clearance, and activity of superoxide dismutase (SOD) were measured at the end of treatment. MAP was significantly reduced in the losartan group compared with the control group (133.3 ± 7.3 vs. 161.5 ± 14.5 mm Hg). Aortic blood flow was significantly higher and aortic vascular resistance was significantly lower in all treated groups than in the control. Urea clearance rose significantly in the l-arginine + losartan group compared with control (393.27 ± 37.58 vs. 218.68 ± 42.03 μL·min–1·100 g–1), as did the activity of SOD (1668.97 ± 244.57 vs. 1083.18 ± 169.96 U/g Hb). Our results suggest that the antihypertensive effect of losartan and l-arginine in SHR is not primarily mediated by increased SOD activity. Also, combined treatment with ATR blockade and l-arginine supplementation has a beneficial effect on renal function that is, at least in part, mediated by increased SOD activity in SHR.
HALL EFFECT, MAGNETORESISTIVITY AND MAGNETIC PROPERTIES OF MgB2 THIN FILMS WITH AlN BUFFER LAYERS
Authors: ILONCA G. , YANG T. R. , POP A. V. , BALINT P. , BODEA M. , MACOCIAN E.
Published: April 2008

MgB 2 thin films were deposited at low temperature substrates, in situ, on c-plane sapphire substrates, with the aluminium nitride (AlN) buffer layers, using the multiple-target sputtering system. The magnetoresistivities were measured using dc-five probe method in applied magnetic field up to 9 Tesla. The upper critical field anisotropy, HC2(T) and irreversibility field H irr (T) versus temperature were determined. The Hall coefficients RH are slightly temperature dependent and positive in the normal state. The critical temperature of 30–32 K and critical current density of 106-107 A/cm 2 at 4.2 K were obtained. Using extracted data, the coherence length ξo, anisotropic coefficient γ and penetration depth λL were calculated.
PARAMETER IDENTIFICATION AND ADAPTIVE SYNCHRONIZATION OF UNCERTAIN HYPERCHAOTIC CHEN SYSTEM
Authors: WANG XINGYUAN , WU XIANGJUN
Published: April 2008

This paper studies the adaptive synchronization and parameter identification of an uncertain hyperchaotic Chen system. Based on the Lyapunov stability theory, an adaptive control law is derived to make the states of two identical hyperchaotic Chen systems asymptotically synchronized. With this approach, the synchronization and parameter identification of the hyperchaotic Chen system with five uncertain parameters can be achieved simultaneously. Theoretical proof and numerical simulations demonstrate the effectiveness and feasibility of the proposed scheme.
DECOHERENCE AND MATTER WAVE INTERFEROMETRY
Authors: QURESHI TABISH , VENUGOPALAN ANU
Published: April 2008

A two-slit interference of a massive particle in the presence of environment-induced decoherence is theoretically analyzed. The Markovian Master equation, derived from coupling the particle to a harmonic-oscillator heat bath, is used to obtain exact solutions which show the existence of an interference pattern. Interestingly, decoherence does not affect the pattern, but only leads to a reduction in the fringe visibility.