bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear Breakup Model for a Liquid Sheet Emanating From a Pressure-Swirl Atomizer
Authors: Ibrahim Ashraf A. , Jog Milind A.
Published: October 2007

Predictions of breakup length of a liquid sheet emanating from a pressure-swirl (simplex) fuel atomizer have been carried out by computationally modeling the two-phase flow in the atomizer coupled with a nonlinear analysis of instability of the liquid sheet. The volume-of-fluid (VOF) method has been employed to study the flow field inside the pressure-swirl atomizer. A nonlinear instability model has been developed using a perturbation expansion technique with the initial amplitude of the disturbance as the perturbation parameter to determine the sheet instability and breakup. The results for sheet thickness and velocities from the internal flow solutions are used as input in the nonlinear instability model. Computational results for internal flow are validated by comparing film thickness at exit, spray angle, and discharge coefficient with available experimental data. The predictions of breakup length show a good agreement with semiempirical correlations and available experimental measurements. The effect of elevated ambient pressure on the atomizer internal flow field and sheet breakup is investigated. A decrease in air core diameter is obtained at higher ambient pressure due to increased liquid-air momentum transport. Shorter breakup lengths are obtained at elevated air pressure. The coupled internal flow simulation and sheet instability analysis provides a comprehensive approach to modeling sheet breakup from a pressure-swirl atomizer.
Viscous microstructural dampers with aligned holes: Design procedure including the edge correction
Authors: Homentcovschi Dorel , Miles Ronald N.
Published: October 2007

The paper is a continuation of the works “Modelling of viscous damping of perforated planar micromechanical structures. Applications in acoustics” [Homentcovschi and Miles, J. Acoust. Soc. Am. 116, 2939–2947 (2004)] and “Viscous Damping of Perforated Planar Micromechanical Structures” [Homentcovschi and Miles, Sensors Actuators, A119, 544–552 (2005)] where design formulas for the case of an offset (staggered) system of holes was provided. The present work contains design formulas for perforated planar microstructures used in MEMS devices (such as proof-masses in accelerometers, backplates in microphones, micromechanical switches, resonators, tunable microoptical interferometers, etc.) in the case of aligned (nonstaggered) holes of circular and square section. The given formulas assure a minimum total damping coefficient (including the squeeze film damping and the direct and indirect resistance of the holes) for an assigned open area. The paper also gives a simple edge correction, making it possible to consider real (finite) perforated planar microstructures. The proposed edge correction is validated by comparison with the results obtained by FEM simulations: the relative error is found to be smaller than 0.04%. By putting together the design formulas with the edge correction a simple integrated design procedure for obtaining viscous perforated dampers with assigned properties is obtained.
Immiscible displacement of oil by water in consolidated porous media due to capillary imbibition under ultrasonic waves
Authors: Hamida Tarek , Babadagli Tayfun
Published: October 2007

Numerous studies done in the last four decades have demonstrated that acoustic stimulation may enhance recovery in oil reservoirs. This technology is not only technically feasible, but also serves as an economical, environmentally friendly alternative to currently accepted enhanced oil recovery (EOR) method. It requires low capital expenditure, and yields almost immediate improvement without any additional EOR agents. Despite a vast body of empirical and theoretical support, this method lacks sufficient understanding to make meaningful and consistent engineering predictions. This is in part due to the complex nature of the physical processes involved, as well as due to a shortage of fundamental/experimental research. Much of what the authors believe is happening within acoustically stimulated porous media is speculative and theoretical. This paper focuses on the effects of ultrasound on the interfacial forces between immiscible fluids. Capillary (spontaneous) imbibition of an aqueous phase into oil (or air)-saturated Berea sandstone and Indiana limestone samples experiments were conducted. Solutions of water, brine (15,000 and 150,000ppmNaCl), anionic surfactant (sodium dodecyl diphenyloxide disulfonate), nonionic surfactant (alcohol ethoxylate) and polymer (xanthan gum) were prepared as the aqueous phase. Both counter-current and co-current geometries were tested. Due to the intrinsically unforced, gentle nature of the process, and their strong dependence on wettability, interfacial tension, viscosity and density, such experiments provide valuable insight into some of the governing mechanisms behind ultrasonic stimulation.
High-frequency diffraction corrections to backscattering cross sections from a rough three-dimensional surface
Authors: Fuks Iosif
Published: October 2007

Diffraction corrections to scalar wave fields at perfectly free and rigid rough surfaces were derived by two iterations of the corresponding integral equations. These diffraction corrections to the pressure or normal velocity (which, in the geometrical optics limit, are doubled at perfectly rigid and free surfaces, respectively) were obtained with an accuracy of ∼1∕k2, where k is the wave number of incidence radiation. Based on these corrections to the surface fields, the backscattering cross sections at normal incidence from the statistically rough Gaussian surfaces were derived. It was found that for the gentle roughness, diffraction results in effective “smoothing” of roughness for rigid and free surfaces and increasing of the backscattering cross sections, but for a rigid surface with steep roughness, the “fictitious” surface can be more rough than the real one, and the diffraction corrections become negative.
On pore-fluid viscosity and the wave properties of saturated granular materials including marine sediments
Authors: Buckingham Michael J.
Published: October 2007

The grain-shearing (GS) theory of wave propagation in a saturated granular material, such as a marine sediment, is extended to include the effects of the viscosity of the molecularly thin layer of pore fluid separating contiguous grains. An equivalent mechanical system consisting of a saturating, strain-hardening dashpot in series with a Hookean spring represents the intergranular interactions. Designated the VGS theory, the new model returns dispersion curves that differ mildly from those of the GS theory at lower frequencies, below 10kHz, where effects due to the viscosity of the pore fluid may be non-negligible. At higher frequencies, the VGS dispersion curves approach those of the GS theory asymptotically. The VGS theory is shown to match the SAX99 dispersion curves reasonably well over the broad frequency band of the measurements, from 1 to 400kHz. This includes the frequency regime between 1 and 10kHz occupied by Schock’s chirp sonar data, where the viscosity of the pore fluid appears to have a discernible effect on the dispersion curves.
Loudness growth in individual listeners with hearing losses: A review
Authors: Marozeau Jeremy , Florentine Mary
Published: October 2007

This letter reanalyzes data from the literature in order to test two loudness-growth models for listeners with hearing losses of primarily cochlear origin: rapid growth and softness imperception. Five different studies using different methods to obtain individual loudness functions were used: absolute magnitude estimation, cross-modality matching with string length, categorical loudness scaling, loudness functions derived from binaural loudness summation, and loudness functions derived from spectral summation of loudness. Results from each of the methods show large individual differences. Individual loudness-growth functions encompass a wide range of shapes from rapid growth to softness imperception.
Perceptual relevance of the temporal envelope to the speech signal in the 4–7kHz band
Authors: Kim Kyung Tae , Choi Jeung-Yoon , Kang Hong Goo
Published: October 2007

The perceptual relevance of adopting the temporal envelope to model the frequency band of 4–7kHz (highband) in wideband speech signal is described in this letter. Based on theoretical work in psychoacoustics, we find out that the temporal envelope can indeed be a perceptual cue for the high-band signal, i.e., a noiseless sound can be obtained if the temporal envelope is roughly preserved. Subjective listening tests verify that transparent quality can be obtained if the model is used for the 4.5–7kHz band. The proposed model has the benefits of offering flexible scalability and reducing the cost for quantization in coding applications.
On the width of a ray
Authors: Rypina Irina I. , Brown Michael G.
Published: October 2007

Consistent with earlier work by Kravtsov and Orlov, a simple general expression for the width of a Fresnel zone δrF in a smooth inhomogeneous environment is derived; this is the diffractive contribution to the width of a ray. In a stratified environment at long range, the general Fresnel zone width expression is shown to reduce approximately to one that is proportional to ∣α∣r(R−r)∕σ where α is the ray stability parameter, σ is the acoustic frequency, r is the range from the source to the field point of interest, and R is the source to receiver range. In a stratified environment on which a weak small-scale perturbation is superimposed, deterministic rays in the background environment that connect fixed end points break up into bundles of micromultipaths at moderate to long range and a second, scattering-induced, contribution δrs to the width of a ray must be considered. It is shown that δrs is proportional to ∣α∣r(R−r) and argued that in a micromultipathing environment the total effective width of a background ray is δrtot=δrF2+δrs2. Theoretical predictions are shown to agree well with travel-time sensitivity kernel calculations.
The room acoustic rendering equation
Authors: Siltanen Samuel , Lokki Tapio , Kiminki Sami , Savioja Lauri
Published: October 2007

An integral equation generalizing a variety of known geometrical room acoustics modeling algorithms is presented. The formulation of the room acoustic rendering equation is adopted from computer graphics. Based on the room acoustic rendering equation, an acoustic radiance transfer method, which can handle both diffuse and nondiffuse reflections, is derived. In a case study, the method is used to predict several acoustic parameters of a room model. The results are compared to measured data of the actual room and to the results given by other acoustics prediction software. It is concluded that the method can predict most acoustic parameters reliably and provides results as accurate as current commercial room acoustic prediction software. Although the presented acoustic radiance transfer method relies on geometrical acoustics, it can be extended to model diffraction and transmission through materials in future.
Perception-based automatic classification of impulsive-source active sonar echoes
Authors: Young Victor W. , Hines Paul C.
Published: October 2007

Impulsive-source active sonar systems are often plagued by false alarm echoes resulting from the presence of naturally occurring clutter objects in the environment. Sonar performance could be improved by a technique for discriminating between echoes from true targets and echoes from clutter. Motivated by anecdotal evidence that target echoes sound very different than clutter echoes when auditioned by a human operator, this paper describes the implementation of an automatic classifier for impulsive-source active sonar echoes that is based on perceptual signal features that have been previously identified in the musical acoustics literature as underlying timbre. Perceptual signal features found in this paper to be particularly useful to the problem of active sonar classification include: the centroid and peak value of the perceptual loudness function, as well as several features based on subband attack and decay times. This paper uses subsets of these perceptual signal features to train and test an automatic classifier capable of discriminating between target and clutter echoes with an equal error rate of roughly 10%; the area under the receiver operating characteristic curve corresponding to this classifier is found to be 0.975.
Modeling the propagation of nonlinear three-dimensional acoustic beams in inhomogeneous media
Authors: Jing Yuan , Cleveland Robin O.
Published: October 2007

A three-dimensional model of the forward propagation of nonlinear sound beams in inhomogeneous media, a generalized Khokhlov-Zabolotskaya-Kuznetsov equation, is described. The Texas time-domain code (which accounts for paraxial diffraction, nonlinearity, thermoviscous absorption, and absorption and dispersion associated with multiple relaxation processes) was extended to solve for the propagation of nonlinear beams for the case where all medium properties vary in space. The code was validated with measurements of the nonlinear acoustic field generated by a phased array transducer operating at 2.5MHz in water. A nonuniform layer of gel was employed to create an inhomogeneous medium. There was good agreement between the code and measurements in capturing the shift in the pressure distribution of both the fundamental and second harmonic due to the gel layer. The results indicate that the numerical tool described here is appropriate for propagation of nonlinear sound beams through weakly inhomogeneous media.
Bactericidal Action of Daptomycin against Stationary-Phase and Nondividing
Staphylococcus aureus
Cells
Authors: Mascio Carmela T. M. , Alder Jeff D. , Silverman Jared A.
Published: October 2007

Most antibiotics with bactericidal activity require that the bacteria be actively dividing to produce rapid killing. However, in many infections, such as endocarditis, prosthetic joint infections, and infected embedded catheters, the bacteria divide slowly or not at all. Daptomycin is a lipopeptide antibiotic with a distinct mechanism of action that targets the cytoplasmic membrane of gram-positive organisms, including
Staphylococcus aureus
. Daptomycin is rapidly bactericidal against exponentially growing bacteria (a 3-log reduction in 60 min). The objectives of this study were to determine if daptomycin is bactericidal against nondividing
S. aureus
and to quantify the extent of the bactericidal activity. In high-inoculum methicillin-sensitive
S. aureus
cultures in stationary phase (10
10
CFU/ml), daptomycin displayed concentration-dependent bactericidal activity, requiring 32 μg/ml to achieve a 3-log reduction. In a study comparing several antibiotics at 100 μg/ml, daptomycin demonstrated faster bactericidal activity than nafcillin, ciprofloxacin, gentamicin, and vancomycin. In experiments where bacterial cell growth was halted by the metabolic inhibitor carbonyl cyanide
m
-chlorophenylhydrazone or erythromycin, daptomycin (10 μg/ml) achieved the bactericidal end point (a 3-log reduction) within 2 h. In contrast, ciprofloxacin (10 μg/ml) did not produce bactericidal activity. Daptomycin (2 μg/ml) remained bactericidal against cold-arrested
S. aureus
, which was protected from the actions of ciprofloxacin and nafcillin. The data presented here suggest that, in contrast to that of other classes of antibiotics, the bactericidal activity of daptomycin does not require cell division or active metabolism, most likely as a consequence of its direct action on the bacterial membrane.
In Vitro Study of
Candida tropicalis
Isolates Exhibiting Paradoxical Growth in the Presence of High Concentrations of Caspofungin
Authors: Sóczó G. , Kardos G. , Varga I. , Kelentey B. , Gesztelyi R. , Majoros L.
Published: October 2007

Paradoxical growth was noted in RPMI 1640 and antibiotic medium 3 in the case of 14 and 1 of 15
Candida tropicalis
strains, respectively, at a caspofungin concentration of 12.5 μg/ml using minimum fungicidal concentration tests. Time-kill assays showed that against isolates killed at lower concentrations, caspofungin at a concentration of 12.5 μg/ml was only fungistatic.
In Immunization with
Plasmodium falciparum
Apical Membrane Antigen 1, the Specificity of Antibodies Depends on the Species Immunized
Authors: Miura Kazutoyo , Zhou Hong , Muratova Olga V. , Orcutt Andrew C. , Giersing Birgitte , Miller Louis H. , Long Carole A.
Published: October 2007

At least a million people, mainly African children under 5 years old, still die yearly from malaria, and the burden of disease and death has increased.
Plasmodium falciparum
apical membrane antigen 1 (PfAMA1) is one of the most promising blood-stage malarial vaccine candidates. However, the allelic polymorphism observed in this protein is a potential stumbling block for vaccine development. To overcome the polymorphism- and strain-specific growth inhibition in vitro, we previously showed in a rabbit model that vaccination with a mixture of two allelic forms of PfAMA1 induced parasite growth-inhibitory antisera against both strains of
P. falciparum
parasites in vitro. In the present study, we have established that, in contrast to a single-allele protein, the antigen mixture elicits primarily antibodies recognizing antigenic determinants common to the two antigens, as judged by an antigen reversal growth inhibition assay (GIA). We also show that a similar reactivity pattern occurs after immunization of mice. By contrast, sera from rhesus monkeys do not distinguish the two alleles when tested by an enzyme-linked immunosorbent assay or by GIA, regardless of whether the immunogen is a single AMA1 protein or the mixture. This is the first report that a malarial vaccine candidate induced different specificities of functional antibodies depending on the animal species immunized. These observations, as well as data available on human immune responses in areas of endemicity, suggest that polymorphism in the AMA1 protein may not be as formidable a problem for vaccine development as anticipated from studies with rabbits and mice.
Immune Distribution and Localization of Phosphoantigen-Specific Vγ2Vδ2 T Cells in Lymphoid and Nonlymphoid Tissues inMycobacterium tuberculosisInfection
Authors: Huang Dan , Shen Yun , Qiu Liyou , Chen Crystal Y. , Shen Ling , Estep Jim , Hunt Robert , Vasconcelos Daphne , Du George , Aye Pyone , Lackner Andrew A. , Larsen Michelle H. , Jacobs William R. , Haynes Barton F. , Letvin Norman L. , Chen Zheng W.
Published: October 2007

Little is known about the immune distribution and localization of antigen-specific T cells in mucosal interfaces of tissues/organs during infection of humans. In this study, we made use of a macaque model ofMycobacterium tuberculosisinfection to assess phosphoantigen-specific Vγ2Vδ2 T cells regarding their tissue distribution, anatomical localization, and correlation with the presence or absence of tuberculosis (TB) lesions in lymphoid and nonlymphoid organs/tissues in the progression of severe pulmonary TB. Progression of pulmonaryM. tuberculosisinfection generated diverse distribution patterns of Vγ2Vδ2 T cells, with remarkable accumulation of these cells in lungs, bronchial lymph nodes, spleens, and remote nonlymphoid organs but not in blood. Increased numbers of Vγ2Vδ2 T cells in tissues were associated withM. tuberculosisinfection but were independent of the severity of TB lesions. In lungs with apparent TB lesions, Vγ2Vδ2 T cells were present within TB granulomas. In extrathoracic organs, Vγ2Vδ2 T cells were localized in the interstitial compartment of nonlymphoid tissues, and the interstitial localization was present despite the absence of detectable TB lesions. Finally, Vγ2Vδ2 T cells accumulated in tissues appeared to possess cytokine production function, since granzyme B was detectable in the γδ T cells present within granulomas. Thus, clonally expanded Vγ2Vδ2 T cells appeared to undergotrans-endothelial migration, interstitial localization, and granuloma infiltration as immune responses toM. tuberculosisinfection.
The TolC-Like Protein of
Neisseria meningitidis
Is Required for Extracellular Production of the Repeats-in-Toxin Toxin FrpC but Not for Resistance to Antimicrobials Recognized by the Mtr Efflux Pump System
Authors: Kamal Nazia , Rouquette-Loughlin Corinne , Shafer William M.
Published: October 2007

A 2.9-kilobase pair locus in
Neisseria meningitidis
was identified as containing transcriptionally linked open reading frames encoding TolC- and HlyD-like proteins. Although the meningococcal TolC protein was required for extracellular production of the repeats-in-toxin (RTX) FrpC toxin, it could not functionally replace the MtrE protein as the outer membrane protein channel for drug export by the MtrC-MtrD-MtrE efflux pump.
A taxonomic and phytogeographical review of some arctic and alpine Senecio species
Authors: Packer John G.
Published: October 2007

A review is presented of the taxonomy of four arctic and (or) alpine species of Senecio, S. conterminus Greenman, S. hyperborealis Greenman, S. resedifolius Less., and S. cymbalarioides Buek. Of these, the first three have been recently claimed by one authority or another to have disjunct distributions between the Alaska–Yukon area and the Rocky Mountains. Investigations based on morphology (including that of the pollen) and cytology confirm the recognition of the four species and have furnished clear evidence for the recognition of a new species, S. ogotorukensis Packer, a description of which is provided. It is concluded from the author's understanding of the taxonomy of these species that none has a disjunct distribution between the Alaska–Yukon area and the Rocky Mountains.
The epiphytic vegetation of Populus balsamifera and its significance as an air pollution indicator in Sudbury, Ontario
Authors: LeBlanc Fabius , Rao Dhruva N. , Comeau Gilberte
Published: October 2007

Indices of atmospheric purity (IAP) of 31 sites, selected in the SO2-polluted as well as in the non-polluted areas around Sudbury were determined on the basis of number, frequency-coverage, and resistance factor of the epiphytes of Populus balsamifera. Based on these indices, arranged into convenient ranges, the investigated area was delimited into five different IAP zones. These zones were then compared with SO2 pollution zones based on the ground-level average concentration of the gas prevailing in the area. From this comparison it is clear that the biological method provides a valid, quick, and economical way for assessing and mapping the long-range effect of pollution of a given area.
Metabolism and the absorption of water by root hairs
Authors: Cailloux Marcel
Published: October 2007

Direct measurements of water uptake on individual root hairs of intact roots have established new parameters of the absorption of water. They show that the velocity of absorption is not proportional to the water stress. Furthermore, absorption takes place only where the main cytoplasmic mass is located in the cell, while no measurable absorption can be found at regions facing the main vacuole. The effects of CO2, age, metabolites, poisons, indicate that there is an intimate correlation between the intensity of metabolism and the velocity of absorption of water. On the other hand, excretion is associated with low metabolism. These new aspects show that absorption of water is a complex phenomenon involving metabolism.
Effects of some respiratory inhibitors on water flux in root hairs of Avena sativa
Authors: Ahmad Mukhtar , Cailloux Marcel
Published: October 2007

Effects of potassium cyanide, sodium azide, and sodium fluoride on water uptake by root hairs of Avena sativa have been investigated. Low concentrations (2 × 10−6 and 2 × 10−5 M) of potassium cyanide accelerate the velocity of water uptake; a decline in the magnitude of water uptake is observed at 2 × 10−4 M and 55% inhibition at 2 × 10−3 M.Azide and fluoride, on the other hand, convert excretion into absorption when applied at low concentrations (3 × 10−4 M and 6 × 10−6 M, respectively) while at increased inhibiting concentrations absorption may be converted into excretion without causing the death of the root hairs.The evidence presented strongly suggests an intimate relationship between respiratory metabolism and absorption of water.
Fine structure of annellophores. III. Monotosporella sphaerocephala
Authors: Hammill Terrence M.
Published: October 2007

In culture, conidiogenesis in Monotosporella sphaerocephala, formerly considered a typical annellophorous species, was inconsistent with the definition of an annellophore. Proliferation involved percurrent growth of intraconidiophore hyphae through the lower layer of bilayered conidium-delimiting septa. A lower septal layer played no role in the formation of a subsequent conidium. Angularly displaced conidia were commonly held on the side of conidiophores by lower septal layers when the layers of conidium-delimiting septa failed to split after conidium secession. Conidium-delimiting septa were laid down early in conidiogenesis, and conidium initials thereafter underwent a great size increase before they seceded as conidia, events inconsistent with the definition of blastic conidium ontogeny made at the Kananaskis Conference on Taxonomy of Fungi Imperfecti.
Fossil coniferous woods from the Oldman Formation (Upper Cretaceous) of Alberta
Authors: Ramanujam C. G. K.
Published: October 2007

The paper deals with a study of four species of coniferous woods recorded for the first time from the Oldman Formation (Campanian) of southern Alberta. These are, Platyspiroxylon parenchimatosum of the Cupressaceae; Taxodioxylon cryptomerioides and T. multiseriatum of the Taxodiaceae; and Podocarpoxylon ajkaense of the Podocarpaceae. Of these, Platyspiroxylon parenchymatosum has affinities with Callitris, while Taxodioxylon cryptomerioides and Podocarpoxylon ajkaense show striking similarities to the wood structure of Cryptomeria and Podocarpus respectively.
Floral development of Alisma triviale
Authors: Singh V. , Sattler R.
Published: October 2007

The primordia of the floral appendages are initiated in acropetal order. They develop in the same order in which they appear but for the petals, which are retarded in their early growth and mature rapidly shortly before anthesis. While the sepal primordia are dorsiventral from their inception, the primordia of other appendages are of nearly radial symmetry and become more or less dorsiventral in their later stages of development. Each petal primordium together with the primordia of a stamen pair arise on one common petal–stamen (CA) primordium. The many pistil primordia arise on three antesepalous gynoecial bulges and the area between them. Thus, in its development the flower exhibits primarily a tricyclic trimerous plan. The floral apices have a two-layered tunica up to the stage of pistil inception. The initiation of all floral appendages occurs by periclinal divisions in the second layer. The third layer (corpus) may contribute, especially in the case of the petal–stamen primordia and the gynoecial bulges. The development of procambium is acropetal. Each primordium receives a single procambial strand shortly after its initiation. Thus, procambial differentiation occurs as a response to primordial inception and not according to the principle of the conservatism of vascular tissue. Additional procambial strands may differentiate as a response to increase in size. The relationships of Alisma to some ranalian families are discussed. Since the floral pattern of Alisma may be considered as a secondary derivation from a trimerous pattern, it does not appear primitive at all. Other primitive features such as apocarpy and lack of fusion of pistil margins are however retained. Thus, Alisma is a good example for heterobathmy.
Developmental studies on leafy spurge (Euphorbia esula). Histology of the adventitious shoot apex
Authors: Ho Teresa W. M. , Raju M. V. S.
Published: October 2007

Histological analyses of adventitious shoot apices of leafy spurge (Euphorbia esula L.) showed variation in the number of mantle layers at various stages of development. The older shoots (stages III and IV) tended to have a larger number of mantle layers than the younger ones (stages I and II) some of which contained two or three layers. The procambial differentiation was acropetal extending from the axis into the leaf primordium and the same pattern was noticed in all stages of development of adventitious buds and shoots. The shoot apex contained larger nuclei and nucleoli in the midsector than in the peripheral sectors and the nuclei in the former had fewer nucleoli. The total volume of nucleoli per nucleus was more in the midsector than in the peripheral sector. However, the ratio of total nucleolar volume to nuclear volume was very similar in all the sectors, suggesting uniform metabolic activity in the adventitious shoot apex.
The relationship between plant sugar concentration, osmotic potential, and frost tolerance in Kharkov MC22 winter wheat. Sugar and frost tolerance
Authors: Green D. G.
Published: October 2007

Increased frost survival after exposure of winter wheat seedlings to solutions of glucose, sucrose, or mannitol was not explained simply by changes in the osmotic potential of the leaves. In some cases either an increase in percentage total carbohydrate and reducing sugars, or a slight decrease in leaf water content increased frost survival. Because of the dependency of osmotic potential and percentage total carbohydrate and reducing sugars on the plant's water status, it is difficult to evaluate their individual importance to frost survival. Because maleic hydroxide is residual it does not have application as a short-term (1-week) growth retardant for increasing frost tolerance in winter wheat.
Influence of some carbon sources on growth of Cochliobolus sativus
Authors: Clark R. V.
Published: October 2007

Four isolates of C. sativus were able to use a number of carbon sources to varying degrees with little evidence of a differential growth response by the isolates. With most carbon sources the response was different when growth on liquid media was compared with that on agar media. Dextrin and L-sorbose were exceptions as dextrin supported good growth with both types and L-sorbose poor with both. Lactose supported the best mycelial growth on liquid media and dextrin the best radial growth and sporulation on agar media when compared with sucrose.
Genera coelomycetum. XIII. Plectronidium gen.nov.
Authors: Raj T. R. Nag
Published: October 2007

Plectronidium gen.nov. is described to accommodate two species: P. minor sp.nov. and P. sinense sp.nov.
Variation and genetics of ribonucleases and phosphodiesterases in conifer seeds
Authors: Mejnartowicz L. , Bergmann F.
Published: October 2007

Using techniques of starch gel electrophoresis, isoenzymes of ribonuclease 11 (RNase, EC 3.1.4.23) and phosphodiesterase I (PDase, EC 3.1.4.1) could be identified in endosperm tissue from dry seeds of three conifer species: Norway spruce (Picea abies). Scots pine (Pinus silvestris), and Douglas fir (Pseudotsuga menziesii). The RNase patterns mostly exhibited a relatively great number of isoenzyme bands as well as a considerable tree-to-tree variation, whereas the PDase system revealed only one enzyme zone in each of the three seed species. Furthermore, an isoenzyme variation within the PDase zones appeared to be very infrequent and could only be detected in Norway spruce and Douglas fir. However, the isoenzyme patterns of RNase as well as PDase showed significant differences between the conifer species. The genetic basis of the intraspecific isoenzyme variations could be easily analyzed, since the test material (seed endosperm) represented haploid tissues resulting from macrogametophytes after fertilization. Hence, it was possible to identify three polymorphic RNase gene loci in Douglas fir seeds, two in Scots pine seeds, and one in Norway spruce seeds. The PDase zone in each conifer species was controlled by one gene locus which revealed allelic forms only in Norway spruce and Douglas fir seeds.
Light and electron microscopic observations of sporangium formation in Albugo Candida (Peronosporales; Oomycetes)
Authors: Khan Saeed R.
Published: October 2007

The formation of sporangia in Albugo Candida was studied using light and scanning and transmission electron microscopy. Their mode of development is blastic and they are not formed by percurrent proliferation as previously suggested.
A new species of Tremella parasitic on Rhytidhysterium rufulum
Authors: Bezerra Jose L. , Kimbrough James W.
Published: October 2007

A new species of basidiomycete parasitizing the ascocarps of Rhytidhysterium rufulum is described and named Tremella rhytidhysterii Bezerra and Kimbrough sp.nov. The mycelial interaction between two species is studied with both light and electron microscopy. The cytological development of basidia and basidiospores is also described. Ultrastructural aspects of the Cryptococcus imperfect state are described and compared with other described species.
Studies on the incidence of coniferous needle endophytes in the Pacific Northwest
Authors: Carroll George C. , Carroll Fanny E.
Published: October 2007

The incidence of internal fungal infections has been scored in coniferous needles from 19 hosts sampled in over 200 sites dispersed throughout western Oregon and southern Washington. Abies grandis, A. magnifica, Picea sitchensis, Pseudotsuga menziesii, and Sequoia sempervirens have proved congenial hosts for needle blade endophytes; petiole fungi are common in all species of Picea and Tsuga sampled. An undescribed taxon in the Hemiphacidiaceae, Chloroscypha spp., Cryptocline spp., Leptostroma spp., Naemacyclus spp., Phomopsis spp., Phyllosticta sp., and several unidentified Coelomycetes with Phoma-like spores were the dominant fungal taxa in the coniferous hosts sampled. The observed patterns of species dominance and diversity suggest that the true population of endophytes has been inadequately sampled in the present study and that an order of magnitude more intensive sampling might be required for real patterns of dominance and diversity to emerge. Many endophytes are restricted to a single coniferous host or to a restricted group of hosts. When similarity coefficients between coniferous species are computed on the basis of their internal needle microfloras, the resultant taxonomic groupings appear similar to those derived from consideration of conventional morphological criteria. Comparison of endophyte incidence with host distribution patterns for Pseudotsuga menziesii reveals that infection rates decrease at high elevations and dry sites.
Cold hardiness of some relatives of hexaploid wheat
Authors: Limin A. E. , Fowler D. B.
Published: October 2007

One hundred and sixty-one accessions, from species which share a common genome with hexaploid wheat (Triticum aestivum E., ABD genome), were rated for cold hardiness following acclimation under fall field conditions. These accessions were from the species T. tauschii (Coss.) Schmal. (D genome); T. monococcum. L., and T. boeoticum Boiss. (A genome); and T. dicoccum Shrank and T. dicoccoides Korn. (AB genome). Accessions from T. tauschii survived the coldest temperatures and had a hardiness level which approached the hardiest hexaploid wheats. The most hardy A genome accessions survived temperatures comparable to hexaploid wheats with low cold hardiness potentials. The remainder of the A and the AB genome wheats were relatively unhardy.
Agaricales on wetland Monocotyledoneae in Canada
Authors: Redhead S. A.
Published: October 2007

Rarely collected Agaricales colonizing wetland monocotyledonae are illustrated and described from Canadian specimens. The occurrence of Gloiocephala menieri, Marasmius caricis, M. limosus, Marasmiellus vaillantii, Mycena bulbosa, and Pholiota graminis in North America is documented. In addition, the first Canadian records of Mycena juncicola and range extensions in Canada for Psathyrella typhae and Mycena stylobates are given. Marasmius flavomerulinus sp.nov. was found on Scirpus in Quebec.
Pathway of movement of apoplastic fluorescent dye tracers through the endodermis at the site of secondary root formation in corn (Zea mays) and broad bean (Vicia faba)
Authors: Peterson Carol A. , Emanuel Mary E. , Humphreys G. B.
Published: October 2007

The apoplastic dyes disodium 4,4′-bis (2-sulfostyryl) biphenyl (Tinopal CBS), a fabric brightener which is bound by cellulose, and trisodium, 3-hydroxy-5,8,10-pyrene trisulfonate (PTS), which is not bound by the walls, were used to trace an apoplastic pathway into the vascular tissues of corn and broad bean roots. The endodermis prevented dye entry into the stele in most regions of roots. However, if the roots were killed prior to dye treatment both dyes entered the steles, indicating that in healthy roots the dyes were confined to the apoplast and were not toxic in the applied concentrations. The more mobile dye, PTS, appeared in the shoots of the plants following a root treatment, indicating that an apoplastic pathway into the stele does exist in the roots. Neither dye penetrated into the steles at the tips of the primary roots. The point of entry in both corn and broad bean was located along the margin of a secondary root which had recently emerged from the epidermis of the primary root. The dyes did not enter the steles of the primary roots during earlier stages of secondary root development, nor did they enter through the secondary root primordia themselves.
In vitro studies on the fine structure of epicuticular leaf wax from Pseudotsuga menziesii
Authors: Lister G. R. , Thair B. W.
Published: October 2007

The epicuticular leaf wax of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) was recrystallized from chloroform solution in vitro. The striated, tubular forms were reconstituted in sizes which included that observed in vivo, indicating that the final dimensions and morphology of the wax crystals are functions of physical properties of the component molecules, rather than an enzyme-dependent polymerization. Subsequent evaluation of all observations and data formed the basis for the scale construction of a model of the tubular wax crystal.
Ultrastructure of Kochiomyces and Triparticalcar zoospores (Spizellomycetales, Chytridiomycetes)
Authors: Barr Donald J. S. , Allan Paula M. E.
Published: October 2007

Kochiomyces and Triparticalcar are recently described genera. Each has unique ultrastructural characteristics in its zoospore. They are classified in the new order Spizellomycetales, in the class Chytridiomycetes. The zoospores of Kochiomyces have a posteriorly positioned nucleus which is ensheathed by microtubules. These microtubules originate from a compound spur on one side of the kinetosome. Microbodies, and one to five mitochondria surround the nucleus. Lipid globules occur in the anterior but these are not associated with microbodies. The Kochiomyces zoospore resembles a primitive blastocladiaceous zoospore which suggests a phylogenetic connection. The zoospores of Triparticalcar have an anteriorly positioned nucleus anchored to the kinetosome by microtubules and a spurlike structure. The spur is 0.8–2.5 μm long and tripartite in cross section. Microbodies are closely associated with lipid globules in the anterior and center of the zoospore. Mitochondria occur not only in the posterior, but also in the center of the zoospore where they often lie close to lipid globules and microbodies.
Studies on North Indian Volvocales. VI. On the life cycle and cytology of a new member of Phacotaceae, Dysmorphococcus sarmaii sp. nov.
Authors: Shyam R.
Published: October 2007

This paper deals with the morphology, reproduction, and cytology of a new species of Dysmorphococcus, viz., Dysmorphococcus sarmaii sp. nov. (Phacotaceae, Volvocales) from India. The lorica of this flagellate displays a remarkable morphological variability in nature as well as in culture under laboratory conditions. The alga is characterised by an anteriorly bilobed pentagonal lorica ornamentated with polygonal pores, a massive globose chloroplast that lacks a pyrenoid and almost completely occupys the protoplast, a prominent red stigma, two contractile vacuoles located anteriorly near the insertion of the flagella, and flagella that are equal to or a little longer than the length of the lorica. The pentagonal lorica of the present taxon differs remarkably from the broadly ovoid to globose lorica of D. variabilis Takeda, D. coccifer Korschikoff, and D. globosus Bold and Starr. The lorica of D. sarmaii is somewhat comparable in shape to D. punctatus Fott because of its bilobed anterior but differs from the latter in its ornamentation. The massive globose chloroplast lacking a pyrenoid in the present alga differs remarkably from the other species of this genus where the chloroplast possesses one or several pyrenoids. In addition, asexual reproduction, which is accomplished by division of the protoplast within the lorica, results in the production of 8–16 zoospores as compared with the earlier record of 2 and 4 zoospores in this genus. The alga is heterothallic and sexual reproduction, which was not known for the earlier described species of the genus Dysmorphococcus, takes place by isogametes produced 16–32(–64) per cell. The chromosome number recorded for D. sarmaii is n = 10.
Effects of high temperature after casing on mushroom production
Authors: Jodon M. H. , Royse D. J. , Schisler L. C.
Published: October 2007

Composts spawned with two cultivars of Agaricus bisporus (Lange) Sing. were subjected to a temperature of 28 ± 0.5 °C for 48 h at four time intervals after casing. Response to heat treatment varied with time of application relative to fruiting induction (pinning). High temperature imposed prior to pinning, while the mycelium was primarily in the vegetative state, resulted in little or no delay in onset of production and significant increases in mushroom size associated with fewer mushrooms per tray. High temperature applied when the mycelium was undergoing primordial formation and extending into pin development resulted in considerable delay in onset of production with no significant effect on mushroom size. Abnormal pins and misshapen caps were observed on all heat treatments. There were significant cumulative yield reductions from most heat treatments after 3 weeks of harvest. Production recovery occurred during the 4th and subsequent weeks of the harvest period with final yields not adversely affected.
Sexual reproduction of Engelmann spruce (Picea engelmannii)
Authors: Singh Hardev , Owens John N.
Published: October 2007

The anatomy and phenology of sexual reproduction of Picea engelmannii Parry from three sites near Prince George, B.C., has been described. The developmental stages at the higher elevation and consequently colder site lagged by 1–2 weeks compared with the lower elevation sites. Pollen mother cells underwent meiosis in mid-May and the five-celled pollen was shed from the end of June to the 1st week of July. The ovules went through the winter rest in the megaspore mother cell stage. The latter underwent meiosis in mid-May to form linear tetrads. The integument was initiated in the postdormancy stages and developed two micropylar prongs which seem characteristic of the genus. The nucellus showed a massive nucellar cap and a pollen chamber formed by the degeneration of cells. The young female gametophyte was surrounded by a spongy tissue which persisted at the chalazal end where the megaspore wall was thickest. The female gametophyte usually bore two archegonia which were fertilised in mid-July (3 weeks after pollination). The embryo developed over the next 3 months. Two main factors which contribute to ovule abortion are failure of pollination and degeneration of embryo during early development.
Fuel characteristics of arctic plant species and simulated plant community flammability by Rothermel's model
Authors: Sylvester T. W. , Wein Ross W.
Published: October 2007

The relative fuel-potentials of 12 northern tundra and forest–tundra ground species of the Mackenzie delta area were evaluated from measured fuel characteristics by simulating a test fire with the Rothermel (1972) fire behavior model. The relative importance of the fuel parameters were in decreasing order: moisture content, biomass, fineness (surface/volume ratio), packing ratio, silica-free ash content, and caloric content. The fuel-potential ratings of the vascular species and of the communities were differentiated primarily by their leaf characteristics. Dead leaves of Calamagrostis canadensis and Eriophorum vaginatum constituted the most flammable fuels measured. Evergreen Ledum palustre and Empetrum nigrum were clearly differentiated from the live vascular species by higher flammability ratings. Of the cryptogam fuels, Cladonia-type lichens were rated intermediate between the above evergreen ericoids and the deciduous woody species (Betula glandulosa, Vaccinium uliginosum, Salix glauca), while Sphagnum sp. was rated comparable to the latter groups. Epilobium angustifolium received the lowest ratings of all species.Subject to the limitations with respect to ether-extractive contents, the relative fuel potential of tundra and forest–tundra plant communities can be rated on measured fuel characteristics, community composition, and the criteria of the Rothermel model. Possible applications of this study were raised, particularly the use of relatively nonflammable plants in land management.
Inducing organ generation in vitro: sepal–petal structures from tobacco flower buds
Authors: McHughen Alan
Published: October 2007

Tobacco (Nicotiana tabacum L. cv. Wisconsin 38) floral buds with sepal primordia only will continue organ production in a normal manner when excised from the plant and placed on the surface of a simple defined medium lacking growth substances. Such a medium is said to be developmentally inert because it does not induce or direct developmental events in the explant but does permit completion of developmental instructions, if any, carried in the explant. If the medium is supplemented with 10.0 ppm kinetin the bud produces a large but variable number of structures having some characteristics of sepals and some characteristics of petals and then continues with the initiation of fairly normal stamens and then carpels. This paper describes these structures and discusses the effect of kinetin on the regulatory systems controlling floral organ generation.
Hydathodes in Physocarpus (Rosaceae: Spiraeoideae)
Authors: Lersten Nels R. , Curtis John D.
Published: October 2007

This is the first anatomical study of hydathodes from subfamily Spiraeoideae. Fresh leaves of Physocarpus opulifolius were cleared, or processed for paraffin and plastic sections and scanning electron microscopy. Each marginal tooth apex bears an achlorophyllous hydathode, which is visible adaxially as a smooth epidermal pad studded with 15–25 small, sunken "water pores" usually covered by an unbroken cuticle. Ordinary stomata are larger, raised, and abaxial. Internally, an epithem of small, loosely arranged cells extends from the adaxial epidermis to the laterally broadened, single vein ending. Bundle and epithem are bounded by the bundle sheath, which extends to the epidermis at the periphery of the pad. Guttation neither was seen naturally nor could it be induced. Cleared leaves of herbarium specimens of the six Physocarpus species showed all degrees of hydathode reduction to complete absence.