bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrasonically determined thickness of long cortical bones: Two-dimensional simulations ofin vitroexperiments
Authors: Moilanen Petro , Talmant Maryline , Bousson Valerie , Nicholson Patrick H. F. , Cheng Sulin , Timonen Jussi , Laugier Pascal
Published: October 2007

Previously it has been demonstrated that cortical bone thickness can be estimated from ultrasonic guided-wave measurements, in an axial transmission configuration, together with an appropriate analytical model. This study considers the impact of bone thickness variation within the measurement region on the ultrasonically determined thickness (UTh). To this end, wave velocities and UTh were determined from experiments and from time-domain finite-difference simulations of wave propagation, both performed on a set of ten human radius specimens (29 measurement sites). A two-dimensional numerical bone model was developed with tunable material properties and individualized geometry based on x-ray computed-tomography reconstructions of human radius. Cortical thickness (CTh) was determined from the latter. UTh data for simulations were indeed in a excellent accordance (root-mean-square error was 0.26mm; r2=0.94, p<0.001) with average CTh within the measurement region. These results indicate that despite variations in cortical thickness along the propagation path, the measured phase velocity can be satisfactorily modeled by a simple analytical model (the A0 plate mode in this case). Most of the variability (up to 85% when sites were carefully matched) observed in the in vitro ultrasound data was explained through simulations by variability in the cortical thickness alone.
Global optimization of distributed output feedback controllers
Authors: Baumann Oliver Nicholas , Elliott Stephen John
Published: October 2007

When the frequency range over which a reduction in vibration is desired is limited to a particular structural mode of vibration, for example, it is shown that a centralized velocity feedback controller can perform better than a decentralized controller for a given level of control effort. The decentralized controller, however, has the desirable properties of scalability and ease of implementation. A number of strategies for clustering the control locations have been proposed to exploit both the performance of the centralized controller and the scalability of decentralized controllers but these have previously been only locally optimal. This paper describes methods by which these distributed controllers may be designed to be globally optimal and gives examples of simulated results of these optimal distributed controllers.
The influence of sensitivity for road traffic noise on residential location: Does it trigger a process of spatial selection?
Authors: Nijland Hans A. , Hartemink Sander , van Kamp Irene , van Wee Bert
Published: October 2007

People move to another house for different reasons. It is sometimes presumed that a process of self-selection might take place on the basis of noise sensitivity, i.e., sensitive people would either leave high noise areas or not move into these areas in the first place. Thus, a “survivor population” would remain in the high noise areas. This research aims to investigate whether such a process can be observed in the Netherlands. The study does not show evidence of a process of self-selection based on noise sensitivity. Nevertheless, the results suggest that noise-sensitive people are less satisfied with their living environment and are more willing to move than those who are not noise sensitive. Due to the limited sample size, external validity is limited.
Transition term method for the analysis of the reflected and the transmitted acoustic signals from water-saturated porous plates
Authors: Belhocine F. , Derible S. , Franklin H.
Published: October 2007

Ultrasound reflection (R) and transmission (T) from an immersed porous plate of QF-20 (a registered trademark of Filtros®, Ferro Corporation) are investigated. Assuming open pores boundary conditions for the theoretical computations, values of the physical constants given by Johnson et al. [D. L. Johnson, D. L. Hemmick, and H. Kojima J. Appl. Phys. 76(1), 115–125 (1994)] are used at first. Comparisons of R and T with experimental results show a discrepancy. It is then assumed that visco-elastic losses exist inside the solid part. When a small imaginary constant part is considered for the bulk moduli, a better fit is obtained between theoretical and experimental values of ∣R∣ and ∣T∣. However, the numerous and very close peaks prevent easy measures of the resonance amplitudes and widths. The transition terms built up from the linear combinations R−T and R+T allow these peaks to be separated. Comparisons between theory and experiments are made. This work validates, in the frequency range where the agreement is good, a method for the location of the symmetrical and antisymmetrical modes of the plate. A discrimination is also possible between modes resulting from the fluid phase motions and from the solid phase motions.
Numerical simulations of fluid-structure interactions in single-reed mouthpieces
Authors: Ricardo da Silva Andrey , Scavone Gary P. , van Walstijn Maarten
Published: October 2007

Most single-reed woodwind instrument models rely on a quasistationary approximation to describe the relationship between the volume flow and the pressure difference across the reed channel. Semiempirical models based on the quasistationary approximation are very useful in explaining the fundamental characteristics of this family of instruments such as self-sustained oscillations and threshold of blowing pressure. However, they fail at explaining more complex phenomena associated with the fluid-structure interaction during dynamic flow regimes, such as the transient and steady-state behavior of the system as a function of the mouthpiece geometry. Previous studies have discussed the accuracy of the quasistationary approximation but the amount of literature on the subject is sparse, mainly due to the difficulties involved in the measurement of dynamic flows in channels with an oscillating reed. In this paper, a numerical technique based on the lattice Boltzmann method and a finite difference scheme is proposed in order to investigate the characteristics of fully coupled fluid-structure interaction in single-reed mouthpieces with different channel configurations. Results obtained for a stationary simulation with a static reed agree very well with those predicted by the literature based on the quasistationary approximation. However, simulations carried out for a dynamic regime with an oscillating reed show that the phenomenon associated with flow detachment and reattachment diverges considerably from the theoretical assumptions. Furthermore, in the case of long reed channels, the results obtained for the vena contracta factor are in significant disagreement with those predicted by theory. For short channels, the assumption of constant vena contracta was found to be valid for only 40% of the duty cycle.
Reliability and frequency specificity of auditory steady-state response detected by phase spectral analysis
Authors: Aoyagi M. , Watanabe T. , Ito T. , Abe Y.
Published: October 2007

Automatic threshold detection techniques are described for auditory steady-state response (ASSR) elicited with a sinusoidally amplitude-modulated tone. The reliability and frequency specificity of ASSR are discussed. When applied to awake adults and detected by phase spectral analysis, 40-Hz ASSR threshold patterns closely resemble their corresponding audiograms. However, 40-Hz ASSR is insufficiently reliable for determining hearing thresholds in young children during sleep. On the other hand, 80-Hz ASSR is detected clearly in sleeping children. Moreover, 80-Hz ASSR threshold patterns also closely resemble the corresponding audiograms. Therefore, 80-Hz ASSR appears to be useful for objective audiometry in children.
An introduction to induced loudness reduction
Authors: Epstein Michael
Published: October 2007

Induced loudness reduction (ILR) is a phenomenon by which a preceding higher-level tone (an inducer tone) reduces the loudness of a lower-level tone (a test tone). The strength of this effect depends on a number of parameters, reviewed here. Some of the implications of ILR on loudness data are presented via the analysis of several studies in which ILR likely resulted in otherwise unexplained biases in data sets. These results serve as examples of the pervasiveness of ILR in loudness measurements and indicate that it is necessary to consider ILR when designing any psychoacoustical experiment in which level varies.
A computationally efficient finite element model with perfectly matched layers applied to scattering from axially symmetric objects
Authors: Zampolli Mario , Tesei Alessandra , Jensen Finn B. , Malm Nils , Blottman John B.
Published: October 2007

A frequency-domain finite-element (FE) technique for computing the radiation and scattering from axially symmetric fluid-loaded structures subject to a nonsymmetric forcing field is presented. The Bérenger perfectly matched layer (PML), applied directly at the fluid-structure interface, makes it possible to emulate the Sommerfeld radiation condition using FE meshes of minimal size. For those cases where the acoustic field is computed over a band of frequencies, the meshing process is simplified by the use of a wavelength-dependent rescaling of the PML coordinates. Quantitative geometry discretization guidelines are obtained from a priori estimates of small-scale structural wavelengths, which dominate the acoustic field at low to mid frequencies. One particularly useful feature of the PML is that it can be applied across the interface between different fluids. This makes it possible to use the present tool to solve problems where the radiating or scattering objects are located inside a layered fluid medium. The proposed technique is verified by comparison with analytical solutions and with validated numerical models. The solutions presented show close agreement for a set of test problems ranging from scattering to underwater propagation.
A computational study of the interaction noise from a small axial-flow fan
Authors: Lu H. Z. , Huang Lixi , So R. M. C. , Wang J.
Published: October 2007

Small axial-flow fans used for computer cooling and many other appliances feature a rotor driven by a downstream motor held by several cylindrical struts. This study focuses on the aerodynamic mechanism of rotor-strut interaction for an isolated fan. The three-dimensional, unsteady flow field is calculated using FLUENT®, and the sound radiation predicted by acoustic analogy is compared with measurement data. Striking differences are found between the pressure oscillations in various parts of the structural surfaces during an interaction event. The suction surface of the blade experiences a sudden increase in pressure when the blade trailing edge sweeps past a strut, while the process of pressure decrease on the pressure side of the blade is rather gradual during the interaction. The contribution of the latter towards the total thrust force on the structure is cancelled out significantly by that on the strut. In terms of the acoustic contributions from the rotor and strut, the upstream rotor dominates and this feature differs from the usual rotor-stator interaction acoustics in which the downstream part is responsible for most of the noise. It is therefore argued that the dominant interaction mechanism is potential flow in nature.
Determination of equivalent sound speed profiles for ray tracing in near-ground sound propagation
Authors: Prospathopoulos John M. , Voutsinas Spyros G.
Published: October 2007

The determination of appropriate sound speed profiles in the modeling of near-ground propagation using a ray tracing method is investigated using a ray tracing model which is capable of performing axisymmetric calculations of the sound field around an isolated source. Eigenrays are traced using an iterative procedure which integrates the trajectory equations for each ray launched from the source at a specific direction. The calculation of sound energy losses is made by introducing appropriate coefficients to the equations representing the effect of ground and atmospheric absorption and the interaction with the atmospheric turbulence. The model is validated against analytical and numerical predictions of other methodologies for simple cases, as well as against measurements for nonrefractive atmospheric environments. A systematic investigation for near-ground propagation in downward and upward refractive atmosphere is made using experimental data. Guidelines for the suitable simulation of the wind velocity profile are derived by correlating predictions with measurements.
Dynamic measurement of room impulse responses using a moving microphone
Authors: Ajdler Thibaut , Sbaiz Luciano , Vetterli Martin
Published: October 2007

A technique for the recording of large sets of room impulse responses or head-related transfer functions is presented. The technique uses a microphone moving with constant speed. Given a setup (e.g., length of the room impulse response), a careful choice of the recording parameters (excitation signal, speed of movement) leads to the reconstruction of all impulse responses along the trajectory. In the case of a moving microphone along a circle, the maximal angular speed is given as a function of the length of the impulse response, its maximal temporal frequency, the speed of sound propagation, and the radius of the circle. As a result of the presented algorithm, head-related transfer functions sampled at 44.1kHz can be measured at all angular positions along the horizontal plane in less than 1s. The presented theory is compared with a real system implementation using a precision moving microphone holder. The practical setup is discussed together with its limitations.
A comparative intelligibility study of single-microphone noise reduction algorithms
Authors: Hu Yi , Loizou Philipos C.
Published: October 2007

The evaluation of intelligibility of noise reduction algorithms is reported. IEEE sentences and consonants were corrupted by four types of noise including babble, car, street and train at two signal-to-noise ratio levels (0 and 5dB), and then processed by eight speech enhancement methods encompassing four classes of algorithms: spectral subtractive, sub-space, statistical model based and Wiener-type algorithms. The enhanced speech was presented to normal-hearing listeners for identification. With the exception of a single noise condition, no algorithm produced significant improvements in speech intelligibility. Information transmission analysis of the consonant confusion matrices indicated that no algorithm improved significantly the place feature score, significantly, which is critically important for speech recognition. The algorithms which were found in previous studies to perform the best in terms of overall quality, were not the same algorithms that performed the best in terms of speech intelligibility. The subspace algorithm, for instance, was previously found to perform the worst in terms of overall quality, but performed well in the present study in terms of preserving speech intelligibility. Overall, the analysis of consonant confusion matrices suggests that in order for noise reduction algorithms to improve speech intelligibility, they need to improve the place and manner feature scores.
Genetic and Phenotypic Identification of Fusidic Acid-Resistant Mutants with the Small-Colony-Variant Phenotype in
Staphylococcus aureus
Authors: Norström Tobias , Lannergård Jonas , Hughes Diarmaid
Published: October 2007

Small-colony variants (SCVs) of
Staphylococcus aureus
are a slow-growing subpopulation whose phenotypes can include resistance to aminoglycosides, defects in electron transport, and enhanced persistence in mammalian cells. Here we show that a subset of mutants selected as SCVs by reduced susceptibility to aminoglycosides are resistant to the antibiotic fusidic acid (FA) and conversely that a subset of mutants selected for resistance to FA are SCVs. Mutation analysis reveals different genetic classes of FA-resistant SCVs. One class, FusA-SCVs, have amino acid substitution mutations in the ribosomal translocase EF-G different from those found in classic FusA mutants. Most of these mutations are located in structural domain V of EF-G, but some are in domain I or III. FusA-SCVs are auxotrophic for hemin. A second class of FA-resistant SCVs carry mutations in
rplF
, coding for ribosomal protein L6, and are designated as FusE mutants. FusE mutants fall into two phenotypic groups: one auxotrophic for hemin and the other auxotrophic for menadione. Accordingly, we have identified new genetic and phenotypic classes of FA-resistant mutants and clarified the genetic basis of a subset of
S. aureus
SCV mutants. A clinical implication of these data is that FA resistance could be selected by antimicrobial agents other than FA.
Estimating Amoxicillin Influx/Efflux in Chinchilla Middle Ear Fluid and Simultaneous Measurement of Antibacterial Effect
Authors: Huang Yue , Yang Zheng , Cartier Linda , Cheung Belinda , Sawchuk Ronald J.
Published: October 2007

Understanding the transport process and the factors that control the influx/efflux of antibiotics between plasma and middle ear fluid is essential in optimizing the antimicrobial efficacy in the treatment of acute otitis media. In this study, an experimental chinchilla model with the application of a microdialysis technique was utilized to evaluate amoxicillin middle ear distribution kinetics. Amoxicillin solutions at various doses were instilled into the middle ear with a simultaneous intravenous bolus dose. Unbound amoxicillin levels were monitored by microdialysis in both ears. Serial phlebotomy provided samples for the measurement of unbound amoxicillin concentration in plasma ultrafiltrates. In infected chinchillas, discrete middle ear fluid samples were plated and cultured to characterize
Streptococcus pneumoniae
growth-kill kinetics. Noncompartmental analysis was used to estimate distributional and elimination clearances assuming linear pharmacokinetics. A nonlinear Michaelis-Menten equation was also used to determine the efflux clearance (from middle ear fluid to plasma) in a mammillary compartment model. No difference was observed in amoxicillin pharmacokinetics between control and infected chinchillas. Influx clearance was (4.6 ± 2.4) × 10
−3
ml/min-kg and significantly lower than the efflux clearance estimated as (19.2 ± 9.7) × 10
−3
ml/min-kg (
P
< 0.002). Nonlinear kinetics was observed in the locally dosed ear. The microdialysis procedure did not interfere with the bacterial growth-kill profile, thereby enabling pharmacokinetic and pharmacodynamic evaluation concurrently. In conclusion, the results suggested that the distribution equilibrium of amoxicillin in the middle ear favors efflux to plasma over influx. An active transport mechanism across middle ear mucosal epithelium may be involved in amoxicillin distribution.
Drugs Designed To Inhibit Human p38 Mitogen-Activated Protein Kinase Activation TreatToxoplasma gondiiandEncephalitozoon cuniculiInfection
Authors: Wei Shuang , Daniel Benjamin J. , Brumlik Michael J. , Burow Matthew E. , Zou Weiping , Khan Imtiaz A. , Wadsworth Scott , Siekierka John , Curiel Tyler J.
Published: October 2007

We recently showed that the pyridinylimidazoles SB203580 and SB202190, drugs designed to block human p38 mitogen-activated protein kinase (MAPK) activation, also inhibited replication of the medically important intracellular parasiteToxoplasma gondiiin cultured human fibroblasts through a direct effect on the parasite. We now show that additional pyridinylimidazole and imidazopyrimidine p38 MAPK inhibitors inhibit intracellularT. gondiireplication in vitro and protect mice against fatalT. gondiiinfection. Mice surviving infection following treatment with p38 MAPK inhibitors were resistant to subsequentT. gondiichallenge, demonstrating induction of protective immunity. Thus, drugs originally developed to block human p38 MAPK activation are useful for treatingT. gondiiinfection without inducing significant immunosuppression. MAPK inhibitors combined with either of the approved anti-Toxoplasmadrugs sulfadiazine and pyrimethamine resulted in improved survival among mice challenged with a fatalT. gondiiinoculum. A MAPK inhibitor also treated mice infected with theMicrosporidiumparasiteEncephalitozoon cuniculi, suggesting that MAPK inhibitors represent a novel class of agents that may have a broad spectrum of antiparasitic activity. Preliminary studies implicate aT. gondiiMAPK homologue as the target of drug action, suggesting possibilities for more-selective agents.
Intrapulmonary Distribution of Intravenous Telavancin in Healthy Subjects and Effect of Pulmonary Surfactant on In Vitro Activities of Telavancin and Other Antibiotics
Authors: Gotfried Mark H. , Shaw Jeng-Pyng , Benton Bret M. , Krause Kevin M. , Goldberg Michael R. , Kitt Michael M. , Barriere Steven L.
Published: October 2007

Steady-state concentrations of telavancin, a novel, bactericidal lipoglycopeptide, were determined in the plasma, pulmonary epithelial lining fluid (ELF), and alveolar macrophages (AMs) of 20 healthy subjects. Telavancin at 10 mg of drug/kg of body weight/day was administered as a 1-h intravenous infusion on three successive days, with bronchoalveolar lavage performed on five subjects, each at 4, 8, 12, and 24 h after the last dose. Plasma samples were collected before the first and third infusions and at 1, 2, 3, 4, 8, 12, and 24 h after the third infusion. The plasma telavancin concentration-time profile was as reported previously. Telavancin (mean ± standard deviation) penetrated well into ELF (3.73 ± 1.28 μg/ml at 8 h and 0.89 ± 1.03 μg/ml at 24 h) and extensively into AMs (19.0 ± 16.8 μg/ml at 8 h, 45.0 ± 22.4 μg/ml at 12 h, and 42.0 ± 31.4 μg/ml at 24 h). Mean concentrations in AMs and plasma at 12 h were 45.0 μg/ml and 22.9 μg/ml (mean AM/plasma ratio, 1.93), respectively, and at 24 h were 42.0 μg/ml and 7.28 μg/ml (mean AM/plasma ratio, 6.67), respectively. Over the entire dosing interval, telavancin was present in ELF and AMs at concentrations up to 8-fold and 85-fold, respectively, above its MIC90for methicillin-resistantStaphylococcus aureus(0.5 μg/ml). Pulmonary surfactant did not affect telavancin's in vitro antibacterial activity. Telavancin was well tolerated. These results support the proposal for further clinical evaluation of telavancin for treating gram-positive respiratory infections.
Effects of Endogenous
d
-Alanine Synthesis and Autoinhibition of
Bacillus anthracis
Germination on In Vitro and In Vivo Infections
Authors: McKevitt Matthew T. , Bryant Katie M. , Shakir Salika M. , Larabee Jason L. , Blanke Steven R. , Lovchik Julie , Lyons C. Rick , Ballard Jimmy D.
Published: October 2007

Bacillus anthracis
transitions from a dormant spore to a vegetative bacillus through a series of structural and biochemical changes collectively referred to as germination. The timing of germination is important during early steps in infection and may determine if
B. anthracis
survives or succumbs to responsive macrophages. In the current study experiments determined the contribution of endogenous
d
-alanine production to the efficiency and timing of
B. anthracis
spore germination under in vitro and in vivo conditions. Racemase-mediated production of endogenous
d
-alanine by
B. anthracis
altered the kinetics for initiation of germination over a range of spore densities and exhibited a threshold effect wherein small changes in spore number resulted in major changes in germination efficiency. This threshold effect correlated with
d
-alanine production, was prevented by an alanine racemase inhibitor, and required
l
-alanine. Interestingly, endogenous production of inhibitory levels of
d
-alanine was detected under experimental conditions that did not support germination and in a germination-deficient mutant of
B. anthracis
. Racemase-dependent production of
d
-alanine enhanced survival of
B. anthracis
during interaction with murine macrophages, suggesting a role for inhibition of germination during interaction with these cells. Finally, in vivo experiments revealed an approximately twofold decrease in the 50% lethal dose of
B. anthracis
spores administered in the presence of
d
-alanine, indicating that rates of germination may be directly influenced by the levels of this amino acid during early stages of disease.
In vitro tuberization of the common potato (Solanum tuberosum) is not a response to the osmotic concentration of the medium
Authors: Lo Fung Mei , Irvine B. R. , Barker W. G.
Published: October 2007

It has been speculated that the rapid tuberization of explanted etiolated stolon nodes of the common potato relates to the osmotic concentration of the medium since this response is speeded by increased sucrose levels up to 12%. This paper demonstrates that the response probably pertains to the energy requirements of the tuberizing explanted stolon and that osmotic concentration is not crucial.
Vegetation patterns and site relationships in the Saskatchewan River delta
Authors: Dirschl Herman J. , Coupland Robert T.
Published: October 2007

This 5-year study attempted to order the landscape pattern of the flood plain complex in the Saskatchewan River delta. The approach involved a stepwise progression, from traditional, subjective classification of the vegetation and mapping by air photo interpretation, to objective classification using association analysis, and final verification by stand and species ordinations through principal component analysis of bog, fen, and mixed forest types. Association analysis efficiently separated the wide vegetational variation according to discontinuities in species composition. The terminal groups of stands showed pronounced affinities for distinct positions in the landscape. The application of principal component analysis to these landscape units showed moisture regime, nutrient status, and pH to be the most significant gradients controlling distribution of species and communities. The interactions of these factors with each other, and with several physical characteristics, have been revealed.
Internal fungi in old-growth Douglas fir foliage
Authors: Bernstein Mary E. , Carroll George C.
Published: October 2007

Culture of surface-sterilized needles from a stand of old-growth Douglas fir trees on the western slope of the Oregon Cascades revealed the presence of latent fungal infections in all needles examined older than 3 years. Scanning electron micrographs of cut needle surfaces seen in transverse section showed occasional intercellular fungal hyphae in the needle parenchyma. Two species of fungi, Phyllosticta sp. and a suspected member of the Hemiphacidiaceae, appeared as the major colonizers of the needle blade; a third species, as yet unidentified, commonly grew out from the needle petiole. Endophytes were widespread in needles throughout the watershed regardless of the elevation and exposure of the individual trees sampled. Similarly, height of the needles in the tree canopy showed little correlation with the frequency of internal infections. Individual needles were cut into 10 segments before culture, and patterns of endophyte distribution within the needles were observed. The data are consistent with the hypothesis that needles are multiply infected during their 1st year. The initial rise in endophyte frequency occurs between November and March on 1st-year needles, a pattern suggesting waterborne spores as agents of infection. Both Phyllosticta and the hemiphacidiaceous fungus are known to produce gloeoid conidia, which are thought to be dispersed by rain. With increasing age, all needle segments become infected with endophytes.
Vegetation and nutrient status of northern Michigan fens
Authors: Schwintzer Christa R.
Published: October 2007

The vegetation, selected characteristics of shallow groundwater, and depth to water were examined in five fens in northern Lower Michigan. The field layer was the dominant stratum in all five fens and contained a total of 85 vascular species with a mean density of 30 vascular species per stand. Carex lasiocarpa was the most prevalent dominant plant and attained a frequency–presence index (FPI) of 8000 of a possible 10 000 and a mean importance value of 33 of a possible 200. Other common dominants in decreasing order of FPI were Carex aquatilis (6640), Myrica gale (4636), and Andromeda glaucophylla (2000). Common subordinates were Hypericum virginicum (2639), Muhlenbergia glomerata (2466), and Campanula aparinoides (1400). The vegetation was relatively homogeneous as indicated by a homogeneity index of 58%.The shallow groundwaters were minerotrophic with pH values ranging from 5.7 to 7.0 and calcium concentrations of 11.0 to 75.0 mg/ℓ. Four of the fens were on floating mats and had relatively stable water levels while the fifth was on a grounded mat and was subject to substantial water level fluctuation.Three previously described alkaline lake-edge kettle-hole 'bog' communities were found to be similar to the fens in species composition and water chemistry.
The ultrastructure and reproductive significance of Monoletes (Pteridospermales) pollen
Authors: Taylor Thomas N.
Published: October 2007

The Carboniferous pteridosperm pollen type Monoletes is described from reproductive organs of differing preservational mode and stratigraphie occurrence. The sporoderm is constructed of two zones: an inner thin lamellated nexine and a thicker alveolate sexine. The ultrastructure of the sporoderm in the area of the proximal suture suggests that germination may have taken place from that region. Distal surface grooves are a consistent feature of the grains examined although grain ontogeny, preservation, and tapetal products may mask their presence. Features of sporoderm infrastructure suggest that Monoletes pollen grains may represent a type transitional between wind and insect pollination.
Austrosequoia wintonensis, a new taxodiaceous cone from Queensland, Australia
Authors: Peters M. D. , Christophel D. C.
Published: October 2007

Anew taxodiaceous ovulate cone, Austrosequoia wintonensis gen. et sp. nov., is described from the area of Winton, Queensland. Australia. The material is believed to come from the Upper Cretaceous but may be younger. The cones have 29–49 cone scales arranged helically around the axis. Each scale has four to seven ovules arranged in a single row. Reproductive shoot leaves are rhomboidal with an incurved apex and a distinct keel. Comparison with extant taxodiaceous genera indicate a strong similarity to Sequoia sempervirens (D.Don) Endl. and Sequoiadendron giganteum (Lindl.) Buchholz. Only limited similarities are observed with species of the Australian endemic Athrotaxis. The deposit also contains conifer pollen cones, ferns, and angiosperm remains which are yet to be described.
Cold tolerance of gametophytes and sporophytes of some cool temperate ferns native to Hokkaido
Authors: Sato Toshiyuki , Sakai Akira
Published: October 2007

To study the phenological adaptation of the life history of ferns to colder regions, the freezing resistance of gametophytes and sporophytes of 14 cool temperate region ferns native to Hokkaido was evaluated in Sapporo. Moreover, drought tolerance of gametophytes of some cool temperate ferns was elucidated. The mature sporophytes were hardy from −5 to −20 °C in most species. However, gametophytes of most species were tolerant to below −40 °C and regrew into normal gametophytes in a month at room temperature. Most of the gametophytes survived well after dehydration to 2–10% water content. The gametophytic generation was more cold tolerant than the sporophytic one. Thus, the gametophytic generation, rather than the sporophytic, might be the generation that survives cold temperature in the field.
Endophytic fungi in foliage of some Cupressaceae in Oregon
Authors: Petrini Orlando , Carroll George
Published: October 2007

Endophytic fungi were isolated from foliage of four host species of Cupressaceae sampled from 19 sites in Oregon. Chamaecyparis lawsoniana and Thuja plicata showed high overall rates of infection (30–50%) while Calocedrus decurrens and Juniperus occidentalis showed lower rates (10–35%). For any particular host, samples from homogeneous stands with a closed canopy showed higher infection rates than those from mixed stands with an open canopy. For a given tree, infection rates tended to increase with increasing foliage age and decreasing distance from the trunk (exceptions are noted in the text below). The most commonly isolated endophytes include Linodochium sp. and Geniculosporium sp. on C. decurrens; Scolecosporiella sp., Nodulisporium sp., Geniculosporium sp., and Chloroscypha alutipes on C. lawsoniana; Retinocyclus abietis anamorph and Hormonema sp. on J. occidentalis; and Chloroscypha seaveri on T. plicata.
A carbon-13 biosynthetic study of stress metabolites from potatoes: the origin of isolubimin
Authors: Stoessl Albert , Stothers J. B.
Published: October 2007

When applied to healthy potato tissue in the absence of fungi, labelled 15-dihydrolubimin was metabolized to isolubimin without dilution of the label. Lubimin obtained in this experiment was completely unlabelled, contra-indicating claims that it is biosynthesized from 15-dihydrolubimin.
Remarkable asymmetries in trifoliolate leaves with particular reference to Medicago
Authors: Small Ernest , Lefkovitch L. P. , Brookes Brenda S.
Published: October 2007

Abaxial pubescence of the trifoliolate leaves of numerous species is asymmetric, with a greater density of trichomes on the portions of the lateral leaflets between their midribs and outer margins (the margins closest to the base of the petiole) than on the remainder of the lateral leaflets or on the central leaflet. This pattern was evaluated statistically in 1250 plants representing 55 species of Medicago, 13 other genera of the Leguminosae, and 5 genera of other plant families. It was found that the magnitude of asymmetry of pubescence is higher in Medicago than in other legumes considered collectively, but the phenomenon is widespread in the Leguminosae. The generality of the pattern in other vascular plant families could not be assessed reliably because of the paucity of nonlegume species with pubescent trifoliolate leaves. However, the pattern is not universal because in Staphylea trifolia (Staphyleaceae) an opposite asymmetry was found. Young trifoliolate leaves of leguminous plants frequently are folded in a complex fashion, which exposes only one-sixth of the surface area, corresponding to the relatively pubescent portions. Higher trichome density on these exposed surfaces may reflect adaptation, perhaps against phytophagous insects or desiccation. However, the pattern may also be explained by a tendency for better trichome development on exposed epidermal surfaces in comparison with surfaces adpressed against each other. A second asymmetry of trifoliolate leaves was also examined: a trend for the width of the relatively pubescent portion of the lateral leaflet to be greater than that of the corresponding portion on the opposite side of the midrib. While this asymmetry was found to be significant, and to be especially well developed in the nonlegumes examined, there are numerous exceptions, and at least in the Leguminosae the tendency is not as strikingly developed as the eccentricity of pubescence.
Osmotic priming of seeds of crop species with polyethylene glycol as a means of enhancing early and synchronous germination at cool temperatures
Authors: Bodsworth S. , Bewley J. D.
Published: October 2007

Polyethylene glycol (PEG) solutions can be used to promote early and synchronous germination of seeds at cool temperatures. The determination of optimum priming levels is an essential prelude to proposed field trials. Priming with solutions of PEG (all at 10 °C) at −10 bars (1 bar = 100 kPa) for 6 days for maize, −10 bars for 2 days for wheat and barley, −10 bars for 1 day for sorghum, and −5 bars for 6 days for soybean has the maximum promotive effect. Air-drying of primed seeds reduces the advantages gained by priming; the longer the period of drying the greater the reduction.
Cytopathological changes induced by potato spindle tuber viroid in Scopolia sinensis
Authors: Paliwal Y. C. , Singh R. P.
Published: October 2007

The mesophyll parenchyma of Scopolia sinensis Hemsl. leaves infected with potato spindle tuber viroid (PSTV) was examined for cytopathological changes. Cells of the systemically infected tissue showed a proliferation of cytoplasmic membranes in the form of sheets or vesicles and generally these membranes and the tonoplast were studded with electron-dense deposits. About 47% of the cells examined contained amorphous electron-dense inclusions in their vacuoles but about 3% of the healthy leaf cells also contained a few such inclusions. The lumen of many mature cells contained small spherical to oval electron-dense bodies interspersed with fibrils. In cells adjoining the local lesions on inoculated leaves, electron-dense bodies were not found and membrane deposits were rare. However, the amorphous inclusions occurred in 52% of these cells examined. Extensive cell wall deposits containing flattened tubules and vesicles were common in cells adjoining local lesions. Only smaller, localized wall deposits were found in cells of the systemically infected tissue and in some cells adjoining local lesions. Cell organelles were generally unaffected in systemically infected tissue except that mitochondria often contained vacuoles filled with an electron-dense deposit. However, degenerating chloroplasts and mitochondria were common in cells adjoining local lesions.
Interactions between a fungal endophyte and gametophyte cells in Psilotum nudum
Authors: Peterson R. L. , Howarth Melanie J. , Whittier Dean P.
Published: October 2007

Mature Psilotum gametophytes found in greenhouse pots containing plants of Hoya, Philodendron, Aspidistra, or Diffenbachia were processed for microscopy. An endophytic fungus was abundant in the rhizoids and in most cortical parenchyma cells except at the growing apices. Although the fungus has not been identified, it is an aseptate fungus with coarse hyphae which occasionally form vesicles. Endophytic fungal hyphae store quantities of lipid which appear to be released into the host cytoplasm upon fungal degeneration. This lipid and the remnants of hyphal cell walls may be used as an energy source by the achlorophyllous gametophyte. Gametophyte cell organelles, including the nucleus, appear to degenerate after fungal breakdown, and the cells presumably die. Although reinfection of cells containing degenerated hyphae was found, it was not particularly common.
Relationships between maximum photosynthetic rates and photosynthetic tolerance of low leaf water potentials
Authors: Bunce James A.
Published: October 2007

Comparisons of photosynthesis and stomatal and mesophyll conductance of CO2 at high leaf water potentials were made in four populations of Taraxacum officinale and in drought tolerant and intolerant individuals within cultivars of four crop species. Plants with the highest rates of photosynthesis at high leaf water potentials were least tolerant of drought, in terms of ability to grow in dry soil, or in maintenance of high photosynthetic rates at low leaf water potentials. Differences in photosynthesis at high leaf water potentials resulted from differences in stomatal conductance, whereas differences in photosynthesis at low leaf water potentials resulted from differences in mesophyll conductance.
Influence des facteurs génétique et physiologique chez le Nicotiana sur la néoformation in vitro de fleurs à partir d'assises cellulaires épidermiques et sous-épidermiques
Authors: Kamate K. , Cousson A. , Trinh T. H , Van K. Tran Thanh
Published: October 2007

Floral neoformation potentialities in various Nicotiana genotypes having different photoperiodic requirements were analyzed in epidermal and subepidermal cell layers from floral branches cultured in vitro with glucose (30 g/L), indoleacetic acid (IAA, 10− M), and kinetine (Kin, 10−6 M). Direct neoformation of flowers occurred in the long-day interspecific hybrid Nicotiana sylvestris × Nicotiana tomentosiformis, but was not obtained with any of the parent species, suggesting that this phenomenon might depend on interactions between those two genotypes, rather than on euperiod. Results obtained following changes in the medium concerned with auxin and cytokinin (naphtalene acetic acid, 3 × 10−7 M or 5 × 10−7 M; benzyl-adenine, 3 × 10−7 M or 5 × 10−7 M) demonstrated the influence of genotype-environment interaction on de novo differentiation of flowers in Nicotiana rustica. [Translated by the journal]
Regeneration of peanut (Arachis hypogaea) plantlets by in vitro culture of immature leaves
Authors: Mroginski L. A. , Kartha K. K. , Shyluk J. P.
Published: October 2007

The in vitro regeneration of buds, shoots, and roots from immature leaves of 3- to 5-day-old peanut (Arachis hypogaea L. cv. Colorado Manfredi) seedlings was studied under defined nutritional, hormonal, and environmental conditions. The first two leaves (2–5 mm in length) removed from aseptically germinated seeds were cultured on Murashige and Skoog medium containing vitamins as in B5 medium and 0.8% agar, supplemented with 12 combinations of naphthaleneacetic acid (NAA) (0.01 to 4 mg/L) and benzyladenine (BA) (1 and 3 mg/L). Bud regeneration occurred in all hormone combinations, but the maximum number of buds was regenerated at a concentration of 1 mg/L each of NAA and BA. Although bud regeneration was maximum with 2- to 5-mm-long leaflets, some success was also obtained with leaflets 8–13 mm long. However, no buds were regenerated when fully expanded leaflets were cultured.Development of buds into shoots was readily achieved by transferring regenerated buds into fresh medium containing 0.01 mg/L NAA and 1 mg/L BA. A few roots were induced to grow when callus with buds was also transferred to medium devoid of hormones. So far, bud regeneration from immature leaves has been induced in vitro in 5 of the 10 cultivars tested.
In vitro studies of adventitious shoot formation in Pinus contorta
Authors: Arnold Sara Von , Eriksson Tage
Published: October 2007

Isolated embryos of Pinus contorta Dougl. ex Loud, were induced to form adventitious buds on a cytokinin-supplemented medium. Further development of the buds required transfer to a cytokininless medium. Both bud induction and development were stimulated by a dilution of the basal culture medium and best growth was obtained if the buds were isolated from the original tissue when stem elongation had started. The growth of these isolated adventitious shoots was further stimulated by adding activated charcoal to the diluted medium. A small percentage of the shoots have been rooted. The capacity for bud formation varied among seeds collected from different regions of British Columbia. This method for induction of adventitious buds on embryos was also applicable to explants of young seedlings.
Vegetative reproduction in the juvenile phase of Ammophila breviligulata
Authors: Krajnyk Irene , Maun M. A.
Published: October 2007

Ammophila breviligulata Fem. was the dominant species with a density of 110 to 150 culms per square metre along Lake Erie shoreline at Rondeau Provincial Park. In the juvenile phase the plants produced underground rhizomes which grew plagiotropically to distances ranging from 129 to 389 cm from the parents and then became orthotropic. The number of nodes on a primary rhizome ranged from 26 to 52 depending on rhizome lengths and each node bore one bud. A small proportion of these buds produced ramets but the rest remained dormant. A chi-square analysis of data showed that leafy shoots occurred in a nonrandom fashion always appearing on the distal end of a primary or secondary rhizome.
Formation of chlamydospores in Gilbertella persicaria
Authors: Powell Martha J. , Bracker Charles E. , Sternshein David J.
Published: October 2007

The cytological events involved in the transformation of vegetative hyphae of the zygomycete Gilbertella persicaria (Eddy) Hesseltine into chlamydospores were studied with light and electron microscopy. Thirty hours after sporangiospores were inoculated into YPG broth, swellings appeared along the aseptate hyphae. Later, septa, traversed by plasmodesmata, delimited each end of the hyphal swellings and compartmentalized these hyphal regions as they differentiated into chlamydospores. Nonswollen regions adjacent to chlamydospores remained as isthmuses. Two additional wall layers appeared within the vegetative wall of the developing chlamydospores. An alveolate, electron-dense wall formed first, and then an electron-transparent layer containing concentrically oriented fibers formed between this layer and the plasma membrane. Rather than a mere condensation of cytoplasm, development and maturation of the multinucleate chlamydospores involved extensive cytoplasmic changes such as an increase in reserve products, lipid and glycogen, an increase and then disappearance of vacuoles, and the breakdown of many mitochondria. Underlying the plasma membrane during chlamydospore wall formation were endoplasmic reticulum, multivesicular bodies, vesicles with fibrillar contents, vesicles with electron-transparent contents, and cisternal rings containing the Golgi apparatus marker enzyme, thiamine pyrophosphatase. Acid phosphatase activity was localized cytochemically in a cisterna which enclosed mitochondria and in vacuoles which contained membrane fragments. Tightly packed membrane whorls and single membrane bounded sacs with finely granular matrices surrounding vacuoles were unique during chlamydospore development. Microbodies were rare in the mature chlamydospore, but endoplasmic reticulum was closely associated with lipid globules. As chlamydospores developed, the cytoplasm in the isthmus became highly vacuolated, lipid globules were closely associated with vacuoles, mitochondria were broken down in vacuoles, unusual membrane configurations appeared, and eventually the membranes degenerated. Unlike chlamydospores, walls of the isthmus did not thicken, but irregularly shaped appositions containing numerous channels formed at intervals on the inside of these walls. The pattern of cytoplasmic transformations during chlamydospore development is similar to events leading to the formation of zygospores and sporangiospores.
Effects of DPX-4189 (2-chloro-N-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)aminocarbonyl)benzenesulfonamide) on anthocyanin synthesis, phenylalanine ammonia lyase activity, and ethylene production in soybean hypocotyls
Authors: Suttle Jeffrey C. , Schreiner Donald R.
Published: October 2007

The effects of the herbicide DPX-4189 (2-chloro-N-((4-methoxy-6-methyl-1,3,5-triazin-2-yl)aminocarbonyl)benzenesulfonamide) on anthocyanin accumulation, phenylalanine ammonia lyase (PAL) activity, and ethylene production in seedlings of soybean (Glycine max L.) were investigated. Application of 1 μg DPX-4189 per plant led to an increase in anthocyanin content in soybean hypocotyls. The increase in anthocyanin content became evident 4 days after application of the herbicide. Accompanying the increase in anthocyanin content was an eightfold increase in extractable PAL activity. An increase in endogenous ethylene evolution also accompanied the increase in anthocyanin content. Application of silver nitrate (an inhibitor of ethylene action) to herbicide-treated seedlings did not prevent the increase in anthocyanin content. Application of 2-chloroethylphosphonic acid (an ethylene-releasing compound) to soybean seedlings stimulated PAL activity but had no effect on anthocyanin content. These results indicated that ethylene did not play a role in DPX-4189 mediated anthocyanin accumulation.