bluuebunny/crossref_metadata_2025_split huggingface dataset:
THERMAL RESISTANCE OF ANTIBIOTIC‐RESISTANT AND ANTIBIOTIC‐SENSITIVE SALMONELLA SPP. ON CHICKEN MEAT
Authors: WALSH C. , DUFFY G. , SHERIDAN J.J. , FANNING S. , BLAIR I.S. , MCDOWELL D.A. 
Published: October 2005

ABSTRACT The aim of this research was to investigate the potential relationship, if any, between the acquisition/possession of antibiotic resistance genes in strains of Salmonella and its resistance to heat stress. Chicken pieces were inoculated with antibiotic sensitive (AS) strains of S. Enteritidis and S. Typhimurium, its laboratory‐acquired antibiotic‐resistant (AR) mutant strains (nalidixic acid and streptomycin), or a multiresistant strain of S. Typhimurium DT104. Half of these samples were heat‐shocked (48C for 30 min) and all were heat‐challenged at 55C for up to 30 min. Samples were then plated on xylose lysine desoxycholate (XLD) and tryptone soya agar (TSA) overpoured with XLD. Heat‐shocked cultures of S. Typhimurium DT104 had significantly higher D‐values (the time required for a 1 log reduction in the number of bacteria) than their non‐heat‐shocked counterparts (P < 0.05). No significant differences were observed between AR and their AS. However, the D‐values for S. Typhimurium DT104 were significantly higher than the D‐values for S. Typhimurium (AS) and S. Enteritidis (AS) (P < 0.05). This study concluded that laboratory‐acquired antibiotic‐resistant mutation did not affect heat resistance of the Salmonella strains studied and suggested a potential link between multiantibiotic resistance and heat resistance in S. Typhimurium DT104.
BIOFILM FORMATION BY SALMONELLA SPP. ON CANTALOUPE MELONS**
Authors: ANNOUS BASSAM A. , SOLOMON ETHAN B. , COOKE PETER H. , BURKE ANGELA 
Published: October 2005

ABSTRACT The ability of two strains of Salmonella to form biofilms on whole cantaloupe melons was investigated. Ten microliters of bacterial suspensions was spot‐inoculated onto cantaloupe melon rinds in pre‐marked areas, and the cantaloupe melons were held at either 10 or 20C. Biofilm formation was monitored using scanning electron microscopy on excised portions of the cantaloupe melon rind at 2, 24, 48, 72 and 144 h postinoculation. Micrographs indicated that biofilm formation occurred rapidly following introduction of cells (2 h at 20C) onto the cantaloupe melon rind. A fibrillar material was visible after just 2 h at 20C, and cells were embedded in extracellular polymeric material after 24 h at either temperature. These results indicate that a human pathogen is capable of forming a biofilm on plant tissue and that biofilm formation may be responsible for the increased recalcitrance of bacteria to aqueous sanitizers.
Compensation strategies for the perturbation of the rounded vowel [u] using a lip tube: A study of the control space in speech production
Authors: Savariaux Christophe , Perrier Pascal , Orliaguet Jean Pierre 
Published: October 2005

A labial perturbation of the French rounded vowel [u] was used to examine the respective weights of the articulatory and acoustic levels in the control of vowel production. A 20-mm-diam lip tube was inserted between the lips of the speakers. Acoustic and x-ray articulatory data were obtained for isolated vowel productions by 11 native French speakers in normal and lip-tube conditions. Compensation abilities were evaluated through accuracy of the F1–F2 pattern. Possible compensations were examined from nomograms using the new model of Fant [ISCLP 92 Proceedings (University of Alberta, Edmonton, 1992)]. Acoustic interpretations of the articulatory changes were made by generating area functions from midsagittal views, used together with a harmonic acoustic model. For the first perturbed trial, immediately after the insertion of the tube, no speaker was able to produce a complete compensation, but clear differences between speakers were observed: Seven of them moved the tongue and hence limited the deterioration of the F1–F2 pattern, whereas the remaining four did not show any pertinent articulatory change. These data support the idea of speaker-specific internal representations of the articulatory-to-acoustic relationships. The results for the following 19 perturbed trials indicate that speakers used the acoustic signal in order to elaborate an optimal compensation strategy. One speaker achieved complete compensation by changing his constriction location from a velo-palatal to a velo-pharyngeal region of the vocal tract. Six others moved their tongues in the right direction, achieving partial acoustic compensation, while the remaining four did not compensate.
The control of speech production thus seems to be directed toward achieving an auditory goal, but completely achieving the goal may be impossible because of speaker-dependent articulatory constraints. It is suggested that these constraints are due more to speaker-specific internal representation of articulatory-to-acoustic relationships rather than to anatomical or neurophysiological limitations. Speech control could thus be ensured partly with the use of this internal representation, and partly—particularly under perturbed conditions—by monitoring the acoustic signal.
Electrode ranking of ‘‘place pitch’’ and speech recognition in electrical hearing
Authors: Nelson David A. , Van Tasell Dianne J. , Schroder Anna C. , Soli Sigfrid , Levine Samuel 
Published: October 2005

The ability to distinguish electrical stimulation of different electrodes on the basis of ‘‘pitch or sharpness’’ was evaluated with an electrode ranking procedure in 14 individual users of the Nucleus cochlear implant. Prior to the electrode ranking test, absolute thresholds and maximum comfortable loudness levels were measured, and loudness balancing was accomplished across all usable electrodes. Performance on the electrode ranking task was defined in terms of d′ per mm of distance between comparison electrodes. Large individual differences were found among cochlear-implant users. In subjects with good to excellent place-pitch sensitivity, the electrode ranking task was limited by a ceiling effect; however, in those with poor to moderate sensitivity d′/mm was relatively constant with spatial separation between electrodes. Place pitch was typically ordered from apical to basal electrodes, i.e., basal electrodes were judged to be higher in pitch than more apical electrodes. However, instances of reversals in place-pitch ordering were seen on some electrodes in some subjects.
Instances were also seen of better electrode ranking in the apical half of the electrode array than in the basal half, and vice-versa. Analyses of the electrode ranking functions in terms of d′ per stimulus indicated that, in some subjects, perfect performance was reached with as little as 0.75 mm between comparison electrodes, the minimum possible. In other subjects, perfect performance was not reached until the spatial separation between comparison electrodes was over 13 mm, more than three quarters of the entire length of the electrode array. Ten of the subjects also participated in a closed-set recognition task of intervocalic consonants. Although the maximum transmitted information for place of consonant articulation (which is based primarily on spectral speech cues) was only 34%, correlations between place-pitch sensitivity and transmitted speech information were as high as 0.71. This was surprising considering the excellent place-pitch sensitivity exhibited by some of the subjects, and may reflect limitations of the Nucleus speech coding strategy for representing spectrally coded speech information. The two prelingual subjects performed notably poorer on the speech task than the postlingual subjects, even though one of the prelingual subjects demonstrated very good place-pitch sensitivity.
Differences in frequency modulation detection and fundamental frequency discrimination between complex tones consisting of resolved and unresolved harmonics
Authors: Plack Christopher J. , Carlyon Robert P. 
Published: October 2005

Three experiments investigated the finding [Shackleton and Carlyon, J. Acoust. Soc. Am. 95, 3529–3540 (1994)] that listeners are very poor at detecting frequency modulation (FM) imposed on complex-tone carriers consisting of harmonics unresolved by the peripheral auditory system. In the first experiment, stimuli consisted of the harmonics of a 62.5- or 250-Hz fundamental (f0) passed through a bandpass filter with cutoff frequencies of 1375 and 1875 Hz. This produced two complexes, one with resolved and one with unresolved harmonics. Threshold measurements confirmed that listeners were very poor at detecting 5-Hz FM imposed on a 200-ms unresolved group, but that performance was relatively good for the resolved group. In addition, the results revealed that, for the unresolved group, thresholds for detecting FM were similar to thresholds for detecting an f0 difference between two static 50-ms complex-tone bursts presented 50 ms apart. The second experiment added a third complex consisting of the harmonics of a 250-Hz f0 passed through a bandpass filter with cutoff frequencies of 5500 and 7500 Hz. These harmonics were also unresolved. Both groups of unresolved harmonics produced similar results, indicating that f0 per se did not determine the results from the first experiment.
The second experiment confirmed the results of the first experiment and in addition showed that, for unresolved harmonics only, there was a large increase in the frequency difference limen (FDL) for changes in f0 as the duration of the tone was decreased from 200 to 50 ms. A final experiment was conducted to examine this duration effect. A fourth complex was added which included various harmonics of a 250-Hz f0 chosen so that no two harmonics were the same between the two observation intervals. This complex was low-pass filtered at 1875 Hz. For this second group of resolved harmonics, listeners could not perform the FDL task by comparing the frequencies of individual harmonics: some computation of f0 was required. FDLs for the two resolved groups showed little variation with duration whereas the FDLs for the unresolved groups increased dramatically as the duration was decreased below 100 ms. Measurement of psychometric functions showed that this result reflected a differential effect of duration on detectability itself, as characterized by d′. It is argued that the poor performance on FM detection for groups of unresolved harmonics reflects a poor performance on f0 extraction over short durations. Furthermore, it is suggested that the differential effects of duration for the resolved and unresolved harmonics may reflect the operation of two distinct pitch mechanisms.
Prediction of signal-to-noise ratio gain for passive higher-order correlation detection of energy transients
Authors: Pflug Lisa A. , Ioup George E. , Ioup Juliette W. , Field Robert L. 
Published: October 2005

In general, higher-order correlation detectors perform well in passive detection for signals of high third- and fourth-order moments. Previous studies by the authors have shown that the normalized third- and fourth-order signal moments are reliable indicators of higher-order correlation detector performance [Pflug et al. (1992b)]. For a deterministic energy transient of known moments through fourth order, it is possible to predict theoretically the amount of gain over an ordinary cross-correlation detector for a bicorrelation or tricorrelation detector applied in a noise environment of known variance. In this paper, formulas that predict detector performance for passive detection at the minimum detectable level are derived. The noise is assumed to be stationary and zero mean with Gaussian correlation central ordinate probability density functions. To test the formulas, SNR detection and gain curves are generated using hypothesis testing and Monte Carlo simulations on a set of test signals. The test signals are created by varying the time width of a pulse-like signal in a sampling window of fixed time duration, resulting in a set of test signals with varying signal moments. Good agreement is found between the simulated and theoretical results.
The effects of observation time (length of detection window) and sampling interval on detector performance are also discussed and illustrated with computer simulations. The prediction formulas indicate that decreasing the observation time or the sampling interval (assuming the signal is sufficiently sampled and the detection window contains the entire signal) improves detection performance. However, the rate of improvement is different for the three detectors. The SNR required to achieve the minimum detectable level of detection performance at a given probability of false alarm (Pfa) decreases with the fourth root of the observation time and sampling interval for the cross-correlation detector, the sixth root for the bicorrelation detector, and the eighth root for the tricorrelation detector. Relative detector performance also varies with Pfa. The probability of detection (Pd) for higher-order detectors degrades less rapidly with decreasing Pfa than the Pd for ordinary correlations. Thus higher-order correlators can be especially appropriate when a very low Pfa is required.
Interaural cross-correlation, lateral fraction, and low- and high-frequency sound levels as measures of acoustical quality in concert halls
Authors: Hidaka Takayuki , Beranek Leo L. , Okano Toshiyuki 
Published: October 2005

Subjective ratings of acoustical quality in concert halls were determined from interviews of conductors, musicians, music critics, and informed listeners during which they were asked to judge the quality of the acoustics and to rank the order of those halls each knew. Subjective ratings on 34 halls were divided into three principal groups: excellent, very good, and less good. No bad halls were studied. The use of the interaural cross-correlation coefficient (IACC) and lateral efficiency (LF) as correlates with the subjective ratings were analyzed in depth. In order to make IACC sensitive to quality ratings, a multi-octave-band average was developed, based on Blauert et al. [Acustica 59, 292 (1986)] and on a subjectively derived set of equal apparent source width (ASW) contours that showed the 0.5-, 1.0-, and 2.0-kHz octave bands to be of equal and principal importance to ASW. This IACC3 was divided into two components, IACCE3, integrated over the first 0.08 s after arrival of the direct sound, and IACCL3, integrated over 0.08–1 s. Subjective judgments were also performed to determine the effects of increased sound levels of symphonic music at frequencies above or below 355 Hz on ASW. It was found that changes in the low-frequency levels (GL) made greater changes in ASW than changes in the high-frequency levels (GH). Because the difference between the low- and high-frequency levels in real halls does not exceed ±5 dB and because both are inversely related to [EDT/Volume], it suffices to measure GL.
Thus IACCL3 and GL appear valuable for determining ASW and the degree of sound-field diffusion in the frequency range from 100 to 3000 Hz for symphonic music in concert halls. The measured quantity [1−IACCE3] alone was found to separate exactly the 17 concert halls for which data were available into three category groups. The constituents of these three groups were the same as those determined from the interviews. The measured lateral fraction (LF) for the 24 halls for which data were available was also compared to the subjective groupings. The average measured values of LF for these halls covered a small range and there were so many overlaps among halls when separation of the halls into three rating groups was attempted that LF was judged not to be suitable for rating the acoustical quality of occupied concert halls.
Binaural advantage for sound pattern identification
Authors: Kidd Gerald , Mason Christine R. , Rohtla Tanya L. 
Published: October 2005

Listeners were trained to identify six patterns of eight sequentially presented 48-ms tone bursts. The variation in frequency forming the patterns was confined to a relatively narrow range around the nominal center frequency, which was either 500, 1000, or 3000 Hz, or was selected randomly on each presentation from a range of 450–3300 Hz. Detection (500 and 3000 Hz only) and identification of the six patterns masked by Gaussian noise was measured in two interaural presentation conditions: masker in-phase and signal in-phase (NoSo), and masker in-phase and signal π rad out-of-phase (NoSπ). The differences in performance in the two interaural presentation conditions for detection and identification are referred to as ‘‘masking-level differences’’ (MLDs) and ‘‘identification-level differences’’ (IDLDs), respectively. At 500 Hz, MLDs and IDLDs were about 11–13 dB. At 3000 Hz, the MLDs and IDLDs were about 1–3 dB. For the random-center-frequency condition, the slopes of the identification-level functions were much shallower for the NoSπ condition than for the NoSo condition so the binaural advantage was large at low signal-to-noise ratios and declined as signal-to-noise ratio increased.
This finding was due to the broad frequency range over which the information was distributed and the decline in the binaural advantage with increasing frequency, a conclusion consistent with that reported for the binaural advantage for speech intelligibility. A second experiment demonstrated that MLDs and IDLDs could be manipulated independently: A 500-Hz tone was added to each element of the 3000-Hz patterns. A large MLD was found—due to detection of the 500-Hz tone—while the identification-level functions were determined solely by the high-frequency information, which produced small IDLDs. Finally, the Gaussian noise masker was replaced by an informational masker comprised of eight randomly chosen eight-tone bursts played simultaneously with the signal-pattern elements which were centered at 1000 Hz. Large amounts of informational masking were found for identification. The slopes of the identification-level functions were much shallower than found for the Gaussian noise masker and a relatively small binaural advantage (about 5 dB) was observed.
Diversification of DNA Sequences in the Symbiotic Genome of
Rhizobium etli
Authors: Flores Margarita , Morales Lucia , Avila Agustín , González Víctor , Bustos Patricia , García Delfino , Mora Yolanda , Guo Xianwu , Collado-Vides Julio , Piñero Daniel , Dávila Guillermo , Mora Jaime , Palacios Rafael 
Published: October 2005

ABSTRACT

Bacteria of the genus
Rhizobium
and related genera establish nitrogen-fixing symbioses with the roots of leguminous plants. The genetic elements that participate in the symbiotic process are usually compartmentalized in the genome, either as independent replicons (symbiotic plasmids) or as symbiotic regions or islands in the chromosome. The complete nucleotide sequence of the symbiotic plasmid of
Rhizobium etli
model strain CFN42, symbiont of the common bean plant, has been reported. To better understand the basis of DNA sequence diversification of this symbiotic compartment, we analyzed the distribution of single-nucleotide polymorphisms in homologous regions from different
Rhizobium etli
strains. The distribution of polymorphisms is highly asymmetric in each of the different strains, alternating regions containing very few changes with regions harboring an elevated number of substitutions. The regions showing high polymorphism do not correspond with discrete genetic elements and are not the same in the different strains, indicating that they are not hypervariable regions of functional genes. Most interesting, some highly polymorphic regions share exactly the same nucleotide substitutions in more than one strain. Furthermore, in different regions of the symbiotic compartment, different sets of strains share the same substitutions. The data indicate that the majority of nucleotide substitutions are spread in the population by recombination and that the contribution of new mutations to polymorphism is relatively low. We propose that the horizontal transfer of homologous DNA segments among closely related organisms is a major source of genomic diversification.
Competition and Coexistence betweenStreptococcus mutansandStreptococcus sanguinisin the Dental Biofilm
Authors: Kreth Jens , Merritt Justin , Shi Wenyuan , Qi Fengxia 
Published: October 2005

ABSTRACTThe human mucosal surface is colonized by the indigenous microflora, which normally maintains an ecological balance among different species. Certain environmental or biological factors, however, may trigger disruption of this balance, leading to microbial diseases. In this study, we used two oral bacterial species,Streptococcus mutansandStreptococcus sanguinis(formerlyS. sanguis), as a model to probe the possible mechanisms of competition/coexistence between different species which occupy the same ecological niche. We show that the two species engage in a multitude of antagonistic interactions temporally and spatially; occupation of a niche by one species precludes colonization by the other, while simultaneous colonization by both species results in coexistence. Environmental conditions, such as cell density, nutritional availability, and pH, play important roles in determining the outcome of these interactions. Genetic and biochemical analyses reveal that these interspecies interactions are possibly mediated through a well-regulated production of chemicals, such as bacteriocins (produced byS. mutans) and hydrogen peroxide (produced byS. sanguinis). Consistent with the phenotypic characteristics, production of bacteriocins and H2O2are regulated by environmental conditions, as well as by juxtaposition of the two species. These sophisticated interspecies interactions could play an essential part in balancing competition/coexistence within multispecies microbial communities.
Stationary-Phase Regulation of RpoS Translation in
Escherichia coli
Authors: Hirsch Matthew , Elliott Thomas 
Published: October 2005

ABSTRACT

In enteric bacteria, adaptation to a number of different stresses is mediated by the RpoS protein, one of several sigma factors that collectively allow a tailored transcriptional response to environmental cues. Stress stimuli including low temperature, osmotic shock, nutrient limitation, and growth to stationary phase (SP) all result in a substantial increase in RpoS abundance and activity. The mechanism of regulation depends on the specific signal but may occur at the level of transcription, translation, protein activity, or targeted proteolysis. In both
Escherichia coli
and
Salmonella enterica
, SP induction of RpoS in rich medium is >30 fold and includes effects on both transcription and translation. Recently, we found that SP control of
rpoS
transcription in
S. enterica
involves repression of the major
rpoS
promoter during exponential phase by the global transcription factor Fis. Working primarily with
E. coli
, we now show that 24 nucleotides of the
rpoS
ribosome-binding site (RBS) are necessary and sufficient for a large part of the increase in
rpoS
translation as cells grow to SP. Genetic evidence points to an essential role for the leader nucleotides just upstream of the Shine-Dalgarno sequence but is conflicted on the question of whether sequence or structure is important. SP regulation of
rpoS
is conserved between
E. coli
and
S. enterica
. When combined with an
fis
mutation to block transcriptional effects, replacement of the
rpoS
RBS sequence by the
lacZ
RBS eliminates nearly all SP induction of RpoS.