bluuebunny/crossref_metadata_2025 huggingface dataset:
Controlled and in situ target strengths of the jumbo squid Dosidicus gigas and identification of potential acoustic scattering sources
Authors: Benoit-Bird Kelly J. , Gilly William F. , Au Whitlow W. L. , Mate Bruce
Published: March 2008

This study presents the first target strength measurements of Dosidicus gigas, a large squid that is a key predator, a significant prey, and the target of an important fishery. Target strength of live, tethered squid was related to mantle length with values standardized to the length squared of −62.0, −67.4, −67.9, and −67.6dB at 38, 70, 120, and 200kHz, respectively. There were relatively small differences in target strength between dorsal and anterior aspects and none between live and freshly dead squid. Potential scattering mechanisms in squid have been long debated. Here, the reproductive organs had little effect on squid target strength. These data support the hypothesis that the pen may be an important source of squid acoustic scattering. The beak, eyes, and arms, probably via the sucker rings, also play a role in acoustic scattering though their effects were small and frequency specific. An unexpected source of scattering was the cranium of the squid which provided a target strength nearly as high as that of the entire squid though the mechanism remains unclear. Our in situ measurements of the target strength of free-swimming squid support the use of the values presented here in D. gigas assessment studies.
The phonation critical condition in rectangular glottis with wide prephonatory gaps
Authors: Tao Chao , Jiang Jack J.
Published: March 2008

The effect of the pressure recovery at glottal exit is introduced to modify the one-mass model. Using the modified one-mass model, the phonation critical condition, including phonation threshold pressure and phonation threshold flow, is analyzed by using the small-amplitude oscillation theory. It is found that the phonation threshold pressure is not sensitive to the change of the prephonatory glottal width at a wide glottal gap. This result agrees with previous experimental observations and suggests that the low slope of dependence of phonation threshold pressure on prephonatory gap found by Chan and Titze [J. Acoust. Soc. Am. 119, 2351–2362 (2006)] could be a consequence of the pressure recovery effect at the glottal exit. In addition, it is predicted that the phonation threshold flow is always significantly increased with the prephonatory gap even at a wide prephonatory glottal gap. Therefore, the phonation threshold flow has an advantage in assessing the phonatory system at a wide prephonatory gap in comparison with the phonation threshold pressure. The phonation threshold flow can be a useful aerodynamic parameter for pathological conditions in which the incomplete glottal gap is often seen.
Waveguide invariant focusing for broadband beamforming in an oceanic waveguide
Authors: Tao Hailiang , Krolik Jeffrey L.
Published: March 2008

The performance of broadband sonar array processing can degrade significantly in shallow-water environments when interference becomes angularly spread due to multipath propagation. Particularly for towed line arrays near endfire, elevation angle spreading of multipath interference often results in masking of weaker sources of interest. While adaptive beamforming in a series of narrow frequency bands can suppress coherent multipath interference, this approach requires long observation times to estimate the required narrowband covariance matrices. To form wideband covariance matrices which can be estimated with less observation time, plane-wave focusing methods have been used to avoid interference covariance matrix rank inflation. This paper extends wideband focusing to the case of coherent multipath interference. The approach presented here, called waveguide invariant focusing (WIF), exploits a robust relationship for the frequency dependence of horizontal wave number differences. Unlike matched-field methods, WIF does not model multipath wave fronts but rather makes the interference appear to occupy the same rank-one subspace across frequency. This permits formation of wideband covariance matrices without interference rank inflation. Simulation experiments in a realistic ocean environment indicate that adaptive beamforming using WIF covariance matrices can provide a significant array gain improvement over conventional adaptive methods with limited observation time.
Ear asymmetries in middle-ear, cochlear, and brainstem responses in human infants
Authors: Keefe Douglas H. , Gorga Michael P. , Jesteadt Walt , Smith Lynette M.
Published: March 2008

In 2004, Sininger and Cone-Wesson examined asymmetries in the signal-to-noise ratio (SNR) of otoacoustic emissions (OAE) in infants, reporting that distortion-product (DP)OAE SNR was larger in the left ear, whereas transient-evoked (TE)OAE SNR was larger in the right. They proposed that cochlear and brainstem asymmetries facilitate development of brain-hemispheric specialization for sound processing. Similarly, in 2006 Sininger and Cone-Wesson described ear asymmetries mainly favoring the right ear in infant auditory brainstem responses (ABRs). The present study analyzed 2640 infant responses to further explore these effects. Ear differences in OAE SNR, signal, and noise were evaluated separately and across frequencies (1.5, 2, 3, and 4kHz), and ABR asymmetries were compared with cochlear asymmetries. Analyses of ear-canal reflectance and admittance showed that asymmetries in middle-ear functioning did not explain cochlear and brainstem asymmetries. Current results are consistent with earlier studies showing right-ear dominance for TEOAE and ABR. Noise levels were higher in the right ear for OAEs and ABRs, causing ear asymmetries in SNR to differ from those in signal level. No left-ear dominance for DPOAE signal was observed. These results do not support a theory that ear asymmetries in cochlear processing mimic hemispheric brain specialization for auditory processing.
Joint time/frequency-domain inversion of reflection data for seabed geoacoustic profiles and uncertainties
Authors: Dettmer Jan , Dosso Stan E. , Holland Charles W.
Published: March 2008

This paper develops a joint time/frequency-domain inversion for high-resolution single-bounce reflection data, with the potential to resolve fine-scale profiles of sediment velocity, density, and attenuation over small seafloor footprints (∼100m). The approach utilizes sequential Bayesian inversion of time- and frequency-domain reflection data, employing ray-tracing inversion for reflection travel times and a layer-packet stripping method for spherical-wave reflection-coefficient inversion. Posterior credibility intervals from the travel-time inversion are passed on as prior information to the reflection-coefficient inversion. Within the reflection-coefficient inversion, parameter information is passed from one layer packet inversion to the next in terms of marginal probability distributions rotated into principal components, providing an efficient approach to (partially) account for multi-dimensional parameter correlations with one-dimensional, numerical distributions. Quantitative geoacoustic parameter uncertainties are provided by a nonlinear Gibbs sampling approach employing full data error covariance estimation (including nonstationary effects) and accounting for possible biases in travel-time picks. Posterior examination of data residuals shows the importance of including data covariance estimates in the inversion. The joint inversion is applied to data collected on the Malta Plateau during the SCARAB98 experiment.
Development and evaluation of methods for assessing tone production skills in Mandarin-speaking children with cochlear implants
Authors: Zhou Ning , Xu Li
Published: March 2008

The aim of the study was (1) to develop methods for evaluating tone production of children with cochlear implants (CIs) who speak Mandarin Chinese and (2) to evaluate the efficacy of using these methods to assess tone production. The subjects included two groups of native-Mandarin-Chinese-speaking children: 14 prelingually deafened children who had received CIs and 61 normal-hearing (NH) children as controls. The acoustic analysis focused on quantification of the degree of differentiation among lexical tones based on tonal ellipses and the overall similarity of tone contours produced by the children with CIs to normative contours derived from the 61 NH children. An artificial neural network was used to recognize tones produced by the children with CIs after trained with tone tokens produced by the NH children. Finally, perceptual judgments on the tone production of both groups were obtained from eight native-Mandarin-speaking NH adults to evaluate the efficacy of the methods. The results showed that all measures using the acoustic, neural-network, and perceptual analyses were highly correlated with each other and could be used to effectively evaluate tone production of children with CIs.
Bottom profiling by correlating beam-steered noise sequences
Authors: Harrison Chris H. , Siderius Martin
Published: March 2008

It has already been established that by cross-correlating ambient noise time series received on the upward and downward steered beams of a drifting vertical array one can obtain a subbottom layer profile. Strictly, the time differential of the cross correlation is the impulse response of the seabed. Here it is shown theoretically and by simulation that completely uncorrelated surface noise results in a layer profile with predictable amplitudes proportional to those of an equivalent echo sounder at the same depth as the array. The phenomenon is simulated by representing the sound sources as multiple random time sequences emitted from random locations in a horizontal plane above a vertical array and then accounting for the travel times of the direct and bottom reflected paths. A well-defined correlation spike is seen at the depth corresponding to the bottom reflection despite the fact that the sound sources contain no structure whatsoever. The effects of using simultaneously steered upward and downward conical beams with a tilted or faceted seabed and multiple layers are also investigated by simulation. Experimental profiles are obtained using two different vertical arrays in smooth and rough bottom sites in the Mediterranean. Correlation peak amplitudes follow the theory and simulations closely.
A variant temporal-masking-curve method for inferring peripheral auditory compression
Authors: Lopez-Poveda Enrique A. , Alves-Pinto Ana
Published: March 2008

Recent studies have suggested that the degree of on-frequency peripheral auditory compression is similar for apical and basal cochlear sites and that compression extends to a wider range of frequencies in apical than in basal sites. These conclusions were drawn from the analysis of the slopes of temporal masking curves (TMCs) on the assumption that forward masking decays at the same rate for all probe and masker frequencies. The aim here was to verify this conclusion using a different assumption. TMCs for normal hearing listeners were measured for probe frequencies (fP) of 500 and 4000Hz and for masker frequencies (fM) of 0.4, 0.55, and 1.0 times the probe frequency. TMCs were measured for probes of 9 and 15dB sensation level. The assumption was that given a 6dB increase in probe level, linear cochlear responses to the maskers should lead to a 6dB vertical shift of the corresponding TMCs, while compressive responses should lead to bigger shifts. Results were consistent with the conclusions from earlier studies. It is argued that this supports the assumptions of the standard TMC method for inferring compression, at least in normal-hearing listeners.
Perturbations of the seismic reflectivity of a fluid-saturated depth-dependent poroelastic medium
Authors: de Barros Louis , Dietrich Michel
Published: March 2008

Analytical formulas are derived to compute the first-order effects produced by plane inhomogeneities on the point source seismic response of a fluid-filled stratified porous medium. The derivation is achieved by a perturbation analysis of the poroelastic wave equations in the plane–wave domain using the Born approximation. This approach yields the Fréchet derivatives of the P–SV- and SH-wave responses in terms of the Green’s functions of the unperturbed medium. The accuracy and stability of the derived operators are checked by comparing, in the time–distance domain, differential seismograms computed from these analytical expressions with complete solutions obtained by introducing discrete perturbations into the model properties. For vertical and horizontal point forces, it is found that the Fréchet derivative approach is remarkably accurate for small and localized perturbations of the medium properties which are consistent with the Born approximation requirements. Furthermore, the first-order formulation appears to be stable at all source–receiver offsets. The porosity, consolidation parameter, solid density, and mineral shear modulus emerge as the most sensitive parameters in forward and inverse modeling problems. Finally, the amplitude-versus-angle response of a thin layer shows strong coupling effects between several model parameters.
Vocalizations produced by humpback whale (Megaptera novaeangliae) calves recorded in Hawaii
Authors: Zoidis Ann M. , Smultea Mari A. , Frankel Adam S. , Hopkins Julia L. , Day Andy , McFarland A. Sasha , Whitt Amy D. , Fertl Dagmar
Published: March 2008

Although humpback whale (Megaptera novaeangliae) calves are reported to vocalize, this has not been measurably verified. During March 2006, an underwater video camera and two-element hydrophone array were used to record nonsong vocalizations from a mother–calf escort off Hawaii. Acoustic data were analyzed; measured time delays between hydrophones provided bearings to 21 distinct vocalizations produced by the male calf. Signals were pulsed (71%), frequency modulated (19%), or amplitude modulated (10%). They were of simple structure, low frequency (mean=220Hz), brief duration (mean=170ms), and relatively narrow bandwidth (mean=2kHz). The calf produced three series of “grunts” when approaching the diver. During winters of the years 2001–2005 in Hawaii, nonsong vocalizations were recorded in 109 (65%) of 169 groups with a calf using an underwater video and single (omnidirectional) hydrophone. Nonsong vocalizations were most common (34 of 39) in lone mother–calf pairs. A subsample from this dataset of 60 signals assessed to be vocalizations provided strong evidence that 10 male and 18 female calves vocalized based on statistical similarity to the 21 verified calf signals, proximity to an isolated calf (27 of 28 calves), strong signal-to-noise ratio, and/or bubble emissions coincident to sound.
Diffuse wave density and directionality in anisotropic solids
Authors: Norris Andrew N.
Published: March 2008

Several general results are derived for diffuse waves in anisotropic solids, including concise expressions for the modal density per unit volume d(ω), and for the participation factor matrix G. The latter is a second-order tensor which describes the orientational distribution of diffuse wave or reverberant energy, and reduces to the identity I under isotropy. Calculations of G for a variety of example materials show significant deviation from I even under moderate levels of anisotropy.
Adaptive feedback cancellation in hearing aids with clipping in the feedback path
Authors: Freed Daniel J.
Published: March 2008

Adaptive linear filtering algorithms are commonly used to cancel feedback in hearing aids. The use of these algorithms is based on the assumption that the feedback path is linear, so nonlinearities in the feedback path may affect performance. This study investigated the effect on feedback canceller performance of clipping of the feedback signal arriving at the microphone, as well as the benefit of applying identical clipping to the cancellation signal so that the cancellation path modeled the nonlinearity of the feedback path. Feedback signal clipping limited the amount of added stable gain that the feedback canceller could provide, and caused misadjustment in response to high-level inputs, by biasing adaptive filter coefficients toward lower magnitudes. Cancellation signal clipping mitigated these negative effects, permitting higher amounts of added stable gain and less misadjustment in response to high-level inputs, but the benefit was reduced in the presence of the highest-level inputs.
Sound field separation technique based on equivalent source method and its application in nearfield acoustic holography
Authors: Bi Chuan-Xing , Chen Xin-Zhao , Chen Jian
Published: March 2008

A technique for separating sound fields using two closely spaced parallel measurement surfaces and based on equivalent source method is proposed. The method can separate wave components crossing two measurement surfaces in opposite directions, which makes nearfield acoustic holography (NAH) applications in a field where there exist sources on the two sides of the hologram surface, in a reverberant field or in a scattered field, possible. The method is flexible in applications, simple in computation, and very easy to implement. The measurement surfaces can be arbitrarily shaped, and they are not restricted to be regular as in the traditional field separation technique. And, because the method performs field separation calculations directly in the spatial domain—not in the wave number domain—it avoids the errors and limitations (the window effects, etc.) associated with the traditional field separation technique based on the spatial Fourier transform method. In the paper, a theoretical description is first given, and the performance of the proposed field separation technique and its application in NAH are then evaluated through experiments.
Evoking biphone neighborhoods with verbal transformations: Illusory changes demonstrate both lexical competition and inhibition
Authors: Bashford James A. , Warren Richard M. , Lenz Peter W.
Published: March 2008

When a recorded verbal stimulus repeats over and over, perceptual changes occur and listeners hear competing forms. These verbal transformations (VTs) were obtained for a phonemically related set of 24 consonant-vowel syllables that varied widely in frequency-weighted neighborhood density (FWND). Listener’s initial transformations involving substitution of consonants versus vowels were strongly correlated with the lexical substitution neighborhood [r=+0.82, p<0.0001]. Interestingly, as stimulus FWND increased, average time spent hearing illusory forms substantially decreased [r=−0.75, p<0.0001]. These results suggest that VTs not only reveal underlying competitors, but also provide a highly sensitive measure of lexical inhibition.
Emergence of
Serratia marcescens
,
Klebsiella pneumoniae
, and
Escherichia coli
Isolates Possessing the Plasmid-Mediated Carbapenem-Hydrolyzing β-Lactamase KPC-2 in Intensive Care Units of a Chinese Hospital
Authors: Cai Jia Chang , Zhou Hong Wei , Zhang Rong , Chen Gong-Xiang
Published: March 2008

Twenty-one
Serratia marcescens
, ten
Klebsiella pneumoniae
, and one
Escherichia coli
isolate with carbapenem resistance or reduced carbapenem susceptibility were recovered from intensive care units (ICUs) in our hospital. Enterobacterial repetitive intergenic consensus-PCR and pulsed-field gel electrophoresis demonstrated that all the
S. marcescens
isolates belonged to a clonal strain and the 10
K. pneumoniae
isolates were indistinguishable or closely related to each other. The MICs of imipenem, meropenem, and ertapenem for all isolates were 2 to 8 μg/ml, except for
K. pneumoniae
K10 (MICs of 128, 256, and >256 μg/ml). Isoelectric focusing, PCRs, and DNA sequencing indicated that all
S. marcescens
isolates produced KPC-2 and a β-lactamase with a pI of 6.5. All
K. pneumoniae
isolates produced TEM-1, KPC-2, CTX-M-14, and a β-lactamase with a pI of 7.3. The
E. coli
E1 isolate produced KPC-2, CTX-M-15, and a β-lactamase with a pI of 7.3. Conjugation studies with
E. coli
(EC600) resulted in the transfer of reduced carbapenem susceptibility compared to that of the original isolates, and only the
bla
KPC-2
gene was detected in
E. coli
transconjugants. Plasmid restriction analysis showed identical restriction patterns among all
E. coli
transconjugants. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and
ompK35/36
gene sequence analysis of outer membrane proteins revealed that
K. pneumoniae
K10 failed to express OmpK36, because of insertional inactivation by an insertion sequence IS
Ecp1
. All these results indicate that KPC-2-producing
S. marcescens
,
K. pneumoniae
, and
E. coli
isolates emerged in ICUs in our hospital. KPC-2 combined with porin deficiency results in high-level carbapenem resistance in
K. pneumoniae
. The same
bla
KPC-2
-encoding plasmid was spread among the three different genera.
Vaccine-Elicited 10-Kilodalton Culture Filtrate Protein-Specific CD8
+
T Cells Are Sufficient To Mediate Protection against
Mycobacterium tuberculosis
Infection
Authors: Wu Ying , Woodworth Joshua S. , Shin Daniel S. , Morris Sheldon , Behar Samuel M.
Published: March 2008

The 10-kDa culture filtrate protein (CFP-10) and 6-kDa early secretory antigen of T cells (ESAT-6) are secreted in abundance by
Mycobacterium tuberculosis
and are frequently recognized by T cells from infected people. The genes encoding these proteins have been deleted from the genome of the vaccine strain
Mycobacterium bovis
bacillus Calmette-Guérin (BCG), and it is hypothesized that these proteins are important targets of protective immunity. Indeed, vaccination with ESAT-6 elicits protective CD4
+
T cells in C57BL/6 mice. We have previously shown that
M. tuberculosis
infection of C3H mice elicits CFP-10-specific CD8
+
and CD4
+
T cells. Here we demonstrate that immunization with a CFP-10 DNA vaccine stimulates a specific T-cell response only to the H-2K
k
-restricted epitope CFP-10
32-39
. These CFP-10
32-39
-specific CD8
+
cells undergo a rapid expansion and accumulate in the lung following challenge of immunized mice with aerosolized
M. tuberculosis
. Protective immunity is induced by CFP-10 DNA vaccination as measured by a CFU reduction in the lung and spleen 4 and 8 weeks after challenge with
M. tuberculosis
. These data demonstrate that CFP-10 is a protective antigen and that CFP-10
32-39
-specific CD8
+
T cells elicited by vaccination are sufficient to mediate protection against tuberculosis.
Interleukin-12 and Host Defense against MurinePneumocystisPneumonia
Authors: Ruan Sanbao , McKinley Laura , Zheng Mingquan , Rudner Xiaowen , D'Souza Alain , Kolls Jay K. , Shellito Judd E.
Published: March 2008

Little is known about the role of the cytokine interleukin-12 (IL-12) inPneumocystispneumonia or its potential use as immunotherapy. We asked whether release of IL-12 is part of the normal host response to this infection and whether local treatment with IL-12 or gene transfer of IL-12 could accelerate clearance of infection. IL-12 was assayed by enzyme-linked immunosorbent assay in normal mice and in mice deficient in IL-12 after inoculation ofPneumocystis carinii.P. carinii-infected mice were treated with local instillation of IL-12 and gene transfer of the IL-12 gene. Inoculation ofP. cariniiinto normal mice evoked a brisk release of IL-12 into lung tissue, and IL-12 P35-deficient mice showed delayed clearance of infection measured by PCR forP. cariniirRNA. In control mice, intranasal recombinant IL-12 accelerated clearance of infection, and this was associated with increased recruitment of inflammatory cells into lavage fluid and increased release of tumor necrosis factor alpha, IL-12, and gamma interferon. Similar results were observed in infected mice depleted of CD4+lymphocytes by using in vivo transfer of the IL-12 gene in a replication-deficient adenoviral vector. IL-12 is part of the normal host response to infection withP. carinii. IL-12 therapy can enhance host resistance to infection in both normal mice and mice depleted of CD4+T lymphocytes. A treatment effect of IL-12 is mediated through enhanced inflammatory cell recruitment into lung tissue and increased tissue concentrations of proinflammatory cytokines.
A Tightly Regulated Surface Protein of
Borrelia burgdorferi
Is Not Essential to the Mouse-Tick Infectious Cycle
Authors: Stewart Philip E. , Bestor Aaron , Cullen Jonah N. , Rosa Patricia A.
Published: March 2008

Borrelia burgdorferi
synthesizes a variety of differentially regulated outer surface lipoproteins in the tick vector and in vertebrate hosts. Among these is OspD, a protein that is highly induced in vitro by conditions that mimic the tick environment. Using genetically engineered strains in which
ospD
is deleted, we demonstrate that this protein is not required for
B. burgdorferi
survival and infectivity in either the mouse or the tick. However, examination of both transcript levels and protein expression indicates that OspD expression is limited to a discrete window of time during
B. burgdorferi
replication within the tick. This time frame corresponds to tick detachment from the host following feeding, and expression of OspD continues during tick digestion of the blood meal but is low or undetectable after the tick has molted. The high level of OspD production correlates to the highest cell densities that
B. burgdorferi
is known to reach in vivo. Although OspD is nonessential to the infectious cycle of
B. burgdorferi
, the tight regulation of expression suggests a beneficial contribution of OspD to the spirochete during bacterial replication within the tick midgut.
A NovelTreponema pallidumAntigen, TP0136, Is an Outer Membrane Protein That Binds Human Fibronectin
Authors: Brinkman Mary Beth , McGill Melanie A. , Pettersson Jonas , Rogers Arthur , Matějková Petra , Šmajs David , Weinstock George M. , Norris Steven J. , Palzkill Timothy
Published: March 2008

The antigenicity, structural location, and function of the predicted lipoprotein TP0136 ofTreponema pallidumsubsp.pallidumwere investigated based on previous screening studies indicating that anti-TP0136 antibodies are present in the sera of syphilis patients and experimentally infected rabbits. Recombinant TP0136 (rTP0136) protein was purified and shown to be strongly antigenic during human and experimental rabbit infection. The TP0136 protein was exposed on the surface of the bacterial outer membrane and bound to the host extracellular matrix glycoproteins fibronectin and laminin. In addition, the TP0136 open reading frame was shown to be highly polymorphic amongT. pallidumsubspecies and strains at the nucleotide and amino acid levels. Finally, the ability of rTP0136 protein to act as a protective antigen to subsequent challenge with infectiousT. pallidumin the rabbit model of infection was assessed. Immunization with rTP0136 delayed ulceration but did not prevent infection or the formation of lesions. These results demonstrate that TP0136 is expressed on the outer membrane of the treponeme during infection and may be involved in attachment to host extracellular matrix components.
“And they told two friends…and so on”: RJ Reynolds’ viral marketing of Eclipse and its potential to mislead the public
Authors: Anderson S J , Ling P M
Published: March 2008

Objective:

To explore viral marketing strategies for Eclipse cigarettes used by the RJ Reynolds Company (Winston-Salem, North Carolina, USA).

Methods:

Analysis of previously secret tobacco industry documents and multimedia materials.

Results:

The failure of RJ Reynolds’ (RJR) 1988 “smokeless” cigarette, Premier, was in part due to widespread bad word of mouth about the product’s flavour, quality and difficulty of use. In 1994 RJR introduced an updated version of Premier, the ostensibly “reduced risk” Eclipse cigarette. RJR developed viral marketing channels to promote Eclipse using (1) exploratory interviews to motivate consumers to spread the word about Eclipse prior to market release, (2) promotional videos featuring positive feedback from test group participants to portray majority consensus among triers, (3) “Tupperware”-like parties for Eclipse where participants received samples to pass around in their social circles and (4) the Eclipse website’s bulletin board as a forum for potential users to discuss the brand in their own words. These strategies targeted the brand’s likeliest adopters, recruited informal and credible representatives of the product unaffiliated with RJR, and controlled the information spread about the product.

Conclusions:

Viral marketing techniques may be particularly useful to promote new tobacco products such as Eclipse that have limited appeal and need a highly motivated audience of early adopters and acceptors. Such techniques help evade the mass rejection that could follow mass promotion, circumvent marketing restrictions, and allow tobacco companies to benefit from health claims made by consumers. Cigarette manufacturers must be held accountable for perceived health benefits encouraged by all promotional activities including viral marketing.
Organ regeneration after median bisection of the sepal primordia of tobacco
Authors: Hicks G. S. , Bell J.
Published: March 2008

Young, newly emergent sepal primordia of tobacco were halved vertically and left attached to their floral meristem. Sterile culture of these meristems on a Linsmaier and Skoog medium for 8 days facilitated regeneration of a new sepal primordium from each original half. Sepal rudiments thus exhibited regulative behavior and are structurally labile.
The life history of shoots of Carex lacustris
Authors: Bernard John M.
Published: March 2008

Most shoots of Carex lacustris live for about 12–14 months, emerging in autumn, overwintering as shoots of up to 50 cm in length, and maturing during the next summer. Others emerge in early spring but both groups die in late autumn. A third class emerges in late July or August, grow to be over 50 cm in length, and die in late autumn, living only 2 or 3 months.Flower initials in this species begin growth in the September–October period and overwinter while about 1.0 cm in length. The shoots that develop inflorescences are in general longer, heavier, and have a greater basal diameter than those shoots which do not flower. More shoots flower if the water level in the marsh was high the previous year.
Ultrastructural characteristics of intergeneric protoplast fusion
Authors: Fowke Larry C. , Rennie P. J. , Kirkpatrick J. W. , Constable F.
Published: March 2008

Protoplasts from mesophyll cells of pea plants and from cultured cells of Vicia were agglutinated with polyethylene glycol (PEG) and subsequently fused upon elution of PEG to form heterokaryons. Ultrastructural studies have shown that during agglutination, localized areas of tight adhesion occurred between plasmalemmae; the membranes remained separated by a narrow gap. The plasmalemmae of adhering protoplasts were relatively smooth. Agglutination and subsequent fusion of protoplasts did not appear to be dependent on a minimum depth of cytoplasm in either partner. Fusion was first observed at the margins of the adhering surfaces. As the areas of cytoplasmic continuity enlarged, the agglutinated plasmalemmae dispersed in the cytoplasm. Cytoplasmic mixing in heterokaryons occurred within 3 h.
Histopathology and histochemistry of sugar beet seedlings resistant and susceptible to Aphanomyces cochlioides
Authors: Herr Leonard J.
Published: March 2008

Hyphae were observed within diseased cortical tissue of hypocotyl lesions of both the susceptible and the resistant varieties but were not detected in symptomless tissues in advance of lesion margins. Hyphae ramified extensively intercellularly and, to a lesser extent, intracellularly. Only in severely diseased beets were hyphae found within the stele. Protoplasts of cortical cells in proximity to hyphae appeared to lose turgor early in pathogenesis; then the cells collapsed and cortical tissue was apparently macerated. Histochemically, cell wall constituents (pectin, hemicellulose, non-cellulosic polysaccharides, lignin, suberin, and cutin) were little changed in diseased beets as compared with healthy beets. Peroxidase and (at times) phenolase activity increased and phenols and quinones accumulated in the stele of diseased plants (adjacent to lesions) to levels above those found in healthy plants. Possibly these phenols and quinones may inhibit colonization of stelar tissues. No differences in accumulation or localization of these substances in the resistant as compared with the susceptible beet varieties were detected by histochemical methods.
Developmental and seasonal patterns of mesophyll ultrastructure in Abies balsamea
Authors: Chabot Jean Fincher , Chabot Brian F.
Published: March 2008

Changes in mesophyll ultrastructure with development and season are described for Abies balsamea. Cells mature sequentially during expansion of the needles. Most cells appear to be fully mature and actively photosynthesizing at the time of budbreak. Tannins appear early and accumulate throughout the growing season. Winter dormancy is marked by an accumulation of lipids throughout the cell, an aggregation of organelles around the nucleus, some loss of chloroplast structure, and a failure of chloroplasts to form starch grains. Reorganization of cell structure and resumption of synthetic activity in the spring occurs about 2 months before budbreak.
Extrafloral nectaries that attract ants in Bromeliaceae: structure and nectar composition
Authors: Galetto Leonardo , Bernardello Luis M.
Published: March 2008

The occurrence of extrafloral nectaries in some species of Bromeliaceae (subfam. Pitcairnioideae) is reported for the first time in the following plants from central and northern Argentina: Deuterocohnia longipetala, Dyckia ferox, Dyckia floribunda, Dyckia aff. gilliesii, Dyckia ragonesei, and Dyckia velascana. Ants are attracted to the extrafloral nectar that is secreted in a very high concentration (around 80% weight to total weight) by nonstructural, nonvascularized nectaries located in the outer verticil of tepals. They do not possess a specially differentiated nectariferous tissue and the exudate is probably secreted through paracytic and anomocytic stomata. Sugars and amino acids were detected in the nectar, but alkaloids, reducing acids, proteins, phenols, and lipids were not. Amino acid concentration ranged from 121.3 to 975 μg/mL. In all the species there was a high concentration of sucrose (97.2–100%), whereas glucose and (or) fructose were absent or present in a small amount (0.4–1.5%). Key words: Bromeliaceae, extrafloral nectaries, structure, nectar composition, ants.
Identification of physiological ecotypes in Hordeum jubatum based on responses to salinity stress
Authors: Wang X. Y. , Suhayda C. G. , Redmann R. E.
Published: March 2008

Variability in salt tolerance of three populations of Hordeum jubatum was determined by analysis of growth parameters and ion relations of plants stressed with Na and Mg salts in solution culture experiments. Two populations from saline meadow habitats (Elstow and Floral) and one from a nonsaline site (University) were salinized with Na2SO4 and MgSO4 at Na:Mg molar ratios of 1:1 and 10:1. Elstow and Floral were more salt tolerant than University. University was more sensitive to the high Mg salt stress (Na:Mg, 1:1) than the high Na salt stress (Na:Mg, 10:1). The leaf area, root dry weight, root to shoot ratio under high Mg salt stress, and the root dry weight under high Na salt stress were significantly less for University plants than for Elstow and Floral plants under equivalent conditions. The greater salt tolerance of the two saline populations was correlated with restriction of Na uptake, more efficient transfer of Ca to young leaves, and the restriction of Mg accumulation in leaf tissue. The results supply evidence for physiologically distinct ecotypes of H. jubatum and indicate that habitat-correlated differences in salt tolerance have evolved in populations of this grass species. Key words: ecotype, Hordeum jubatum, ion balance, magnesium sulphate, salt tolerance, sodium sulphate, soil–plant relations, soil salinity.
Peanut peroxidase and the anionic component
Authors: O'Donnell J. P. , Huystee R. B. van
Published: March 2008

Secreted peroxidase (EC 1.11.1.7) from cultured peanut (Arachis hypogaea L.) cells has two main isozymes, one cationic and one anionic. The cationic isozyme has been studied intensively owing to its greater availability. However, the several-fold lower yield of anionic peroxidase has limited study of this isozyme. In the current investigation, the yield of this isozyme from the spent medium is quantified. In addition, feedback by cationic peroxidase on its own synthesis is investigated. Key words: peanut, peroxidase, anionic, cationic, yield, feedback.
Cytotaxonomy of the Festuca spp. from Patagonia
Authors: Dubcovsky Jorge , Martínez Arturo J.
Published: March 2008

Chromosome number and karyotypes of Festuca argentina (2n = 28), Festuca magellanica (2n = 42 and 2n = 56), and Festuca purpurascens (2n = 42) are described here for the first time, as well as new data on the karyotype of Festuca contracta (2n = 42). Multivariate analysis based on chromosome size and shape showed significant (p < 0.05) differences among these species but not among the populations of F. magellanica analyzed. The correlation between a distance matrix among all the Patagonian species based on nine karyotype parameters and one based on morphoreproductive characters was significant (r = 0.60, p < 0.01) but it was not significant when compared with vegetative characters (r = 0.25, p > 0.05). The morphoreproductive and cytological data supported the classification of the Patagonian species in four different subgenera reflecting that the Patagonian Festuca spp. had different phylogenetic origins. Key words: Festuca, karyotype, cytotaxonomy.
Biological control of Fusarium wilt of carnation with a nonpathogenic isolate of Fusarium oxysporum
Authors: Postma J. , Rattink H.
Published: March 2008

The nonpathogenic isolate 618-12 of Fusarium oxysporum, wild type as well as a benomyl-resistant mutant, suppressed Fusarium wilt (F. o. f.sp. dianthi) in a susceptible cultivar of carnation by 80%. Two other nonpathogenic isolates had a similar effect. Suppression by isolate 618-12 occurred only when antagonist and pathogen were both added to the soil but not if they were introduced at a different location (one in the stem, the other in the soil). Thus systemic induced resistance could not be demonstrated. In treatments where isolate 618-12 and the pathogen were both introduced into the soil, fewer plants showed symptoms, disease severity was less, and colonization by the pathogen was less extensive than after inoculation with the pathogen alone. After soil inoculation, the nonpathogenic isolate 618-12 was recovered from the stem, sometimes at a height of 60 cm. Key words: colonization, carnation stem, soil.
Variation within and between populations of Fusarium oxysporum based on vegetative compatibility and mitochondrial DNA
Authors: Gordon T. R. , Okamoto D.
Published: March 2008

Two hundred isolates of Fusarium oxysporum, 100 from each of two different locations, were collected from agricultural field soils in the San Joaquin Valley of California. These isolates comprised 39 different vegetative compatibility groups. Based on the frequency distribution of vegetative compatibility groups, populations of F. oxysporum at the two collection sites were different. At least one isolate from each vegetative compatibility group was examined for polymorphisms in mitochondrial DNA. A total of 41 differences in mitochondrial DNA were identified, each of which was treated as a character and scored as present or absent in each strain. There were 11 unique combinations (haplotypes) of the 41 characters. Three mitochondrial DNA haplotypes were common to both sites and the remaining eight occurred at only one of the two sites. Isolates in the same vegetative compatibility group were always associated with the same mitochondrial DNA haplotype. Many isolates in different vegetative compatibility groups also shared a common mitochondrial DNA haplotype. Fusarium oxysporum f.sp. melonis, cause of Fusarium wilt of muskmelon, was associated with the same mitochondrial DNA haplotype as eight vegetative compatibility groups of F. oxysporum that were not pathogenic to muskmelon. This result may indicate that either the pathogen was a recent derivative of nonpathogenic strains at the same location or avirulent strains have been derived from the pathogen. Key words: anastomosis, fungi, heterokaryon, Fusarium wilt.
Élaboration d'un coefficient de résistance au gui chez le chêne
Authors: Hariri E. B. , Jeune B. , Baudino S. , Urech K. , Sallé G.
Published: March 2008

The reactions of oak to mistletoe (Viscum album L.) were studied using about 100 sensitive and susceptible oak twigs belonging to three species of oak: Quercus robur, Quercus rubra, and Quercus petraea. The main parameters likely to be involved in the resistance mechanism to mistletoe were measured on longitudinal radial sections. After conducting several principal component analyses and discriminant analyses, four variables were shown to have high discriminant values: thickness of the cortex, density of polyphenol-containing cells, thickness of the first layers of fibers, and thickness of collenchyma. Statistical analyses were performed using a large number of samples to define a discriminating function linking the four variables and to propose a resistance coefficient. The significance of such a coefficient for forest managers and pharmacologists is discussed in relation to their own needs. Key words: Viscum album, Quercus, resistance coefficient, mistletoe.
Characterization and comparison of macrofungal communities in an Alnus tenuifolia and an Alnus crispa forest in Alaska
Authors: Brunner Ivano , Brunner Franziska , Laursen Gary A.
Published: March 2008

Occurrence of macrofungal sporocarps, vascular plants, mosses, and lichens was recorded during the growing season of 1987 in an Alnus tenuifolia and an Alnus crispa forest near Fairbanks, Alaska. In total, 131 macrofungal species were observed, with 57 species recorded for the A. tenuifolia forest, 95 species for the A. crispa forest, and 21 species common to both. The ratio of macrofungal species to species of plants and lichens at the A. tenuifolia site was 2.0, but it was 3.3 at the A. crispa site. Similarity of macrofungi and plant–lichens ranged between 62 and 82% among plots within the same study sites and between 17 to 30% among plots between various study sites. Species–area curves for both study sites indicate that an area of 3000 m2 should contain the representative macrofungal community. The predominant and characteristic macrofungi within the A. tenuifolia forest were the ectomycorrhizal species Hebeloma cf. crustuliniforme and Alpova diplophloeus and the saprobic species Clitocybe cf. catervata. Within the A. crispa forest, the predominant and characteristic ectomycorrhizal species were Russula alnicrispae and Russula subarctica and the saprobic species Plicatura nivea and Clitocybe subalutacea. Common and frequent species in both forest types were Naucoria escharoides s.l., Polyporus varius, Lycoperdon perlatum, Coprinus domesticus, and Mycena speirea. Key words: Alaska, Alnus tenuifolia forest, Alnus crispa forest, macrofungal communities, mycoecology.
Alvar vegetation in Canada: a multivariate description at two scales
Authors: Belcher J. W. , Keddy P. A. , Catling P. M.
Published: March 2008

Alvars are areas with a distinctive dry grassland vegetation growing in thin soil over level limestone, and they are documented in Scandinavia, the eastern United States, and central Canada. Ordination and classification analysis techniques were used to describe alvar vegetation in Canada at two scales: within one alvar and among four alvar sites. Within one alvar, changes in species composition corresponded to changes in soil depth and biomass. There were two main vegetation types: (i) alvar meadows with complete vegetation cover and (ii) rock flats with incomplete vegetation cover over limestone rock. Among alvars, species composition was related primarily to geographic location. The southern site was distinct from the eastern and northern sites. Relationships between soil depth, plant biomass, and vegetation could also be detected. At within and among alvar scales, tall perennial graminoids dominated sites with deep soil while small annuals and stress-tolerant perennials dominated shallow soil sites. Average biomass levels were strongly positively correlated with soil depth across vegetation types. Average species richness was curvilinearly related to biomass. Our results describe Canadian alvar vegetation and illustrate important differences among alvar sites, showing that a number of these sites need protection to conserve alvar vegetation. Key words: grassland, drought, soil depth, species richness, biomass, conservation.
Nutritional response of loblolly pine exposed to ozone and simulated acid rain
Authors: Baker Timothy R. , Allen H. Lee , Schoeneberger Michele M. , Kress Lance W.
Published: March 2008

The effects of ozone and simulated acid rain on the aboveground nutrient composition of loblolly pine (Pinustaeda L.) seedlings were studied in a 2-year open-top chamber experiment in the Piedmont of North Carolina. Multivariate analysis of variance tests indicated significant ozone response in the 2nd year but no significant simulated acid rain effect in either year. No interaction among treatments was detectable. Seedlings responded to increasing ozone exposures with increasing concentrations of nitrogen, phosphorus, potassium, magnesium, and calcium in the stem, branches, and foliage. The response of increased nutrient concentration was associated with decreased total biomass accumulation. The nutritional responses were most prominent in late season flushes of foliage and are probably related to ozone-induced premature abscission of early-season flushes. High nutrient concentrations in the stem, branches, and late-season flushes of trees exposed to elevated ozone levels suggest retranslocation and slower growth rates resulted in better aboveground nutrient status and lower nutrient demand from the soil.
Techniques to study the cell cycle in conifer shoot apical meristems
Authors: Grob J.A. , Owens J.N.
Published: March 2008

A method is presented to determine the mitotic index of conifer shoot apical meristems in a rapid and standardized manner using permanent Feulgen-stained squash preparations observed with a series of horizontal scans at fixed vertical intervals. Interpretation and application of mitotic index and its relationship to the cell cycle are discussed. Methods used to label nuclei within conifer apical meristems with tritiated thymidine and procedures that may improve incorporation of label and decrease cellular damage are discussed. The percentage of cells in S stage was determined using autoradiography after apices were immersed in a solution containing 203.5 kBq/mL tritiated thymidine in 1% DMSO for 2 h. With nuclei in S stage identified by autoradiography, G1 and G2 nuclei were visually identified based on Feulgen staining intensity and nuclear area. Using these techniques it was determined that loblolly pine (Pinustaeda L.) apical meristems in rapid neoformed needle initiation had 75% of their cells in G1, 14.8% in S, 4.7% in G2, and 4.6% in mitosis. The relationships between the size of nuclei, the initiation of DNA synthesis, and zonation in the apical dome are discussed.