bluuebunny/crossref_metadata_2025 huggingface dataset:
Is plasticity in partitioning of photosynthetic resources between and within leaves important for whole‐plant carbon gain in canopies?
Authors: PONS T. L. , ANTEN N. P. R.
Published: December 2004

The significance for whole‐plant carbon gain of plasticity in between‐leaf and within‐leaf partitioning of photosynthetic resources was investigated using an experimental and modelling approach. Lysimachia vulgaris L. was grown at two contrasting stand densities and two levels of nutrient availability in a glasshouse. Whole‐plant daily C gain was calculated for the four treatments. The importance of the two forms of plasticity in photosynthetic resource partitioning was investigated by switching distribution patterns of leaf nitrogen and photosynthetic capacity per unit chlorophyll between plants in the two stand densities and recalculating whole‐plant C gain, which was used as a measure of fitness.

The plants had a high photosynthetic capacity per unit leaf area in top leaves in the dense stands, and a low capacity in bottom leaves. The distribution over plant height was more homogeneous in the open stands. This plasticity in between‐leaf resource partitioning was not very important for whole‐plant C gain, provided the plants had a dense‐canopy type of partitioning. It is argued, however, that this result of the model calculations is valid only for low, but not high, nutrient availability.

Photosynthetic capacity per unit chlorophyll, a parameter representative of within‐leaf partitioning of photosynthetic resources between capacity and light harvesting, also showed plasticity in response to stand density. High values were found in open stands and in the top leaves in dense stands, whereas a low capacity per unit chlorophyll was found in shaded bottom leaves in dense stands. Plasticity in this trait was also not very important for C gain of plants in stands of contrasting densities. Here the condition was that plants have a distribution pattern found for open‐stand plants. However, in the case of subordinate plants that have all their leaves in the shade cast by their taller neighbours, adjustment of photosynthetic capacity per unit chlorophyll to the level of irradiance is much more important for whole‐plant C gain.
Ecophysiological constraints on spore establishment in bryophytes
Authors: WIKLUND K. , RYDIN H.
Published: December 2004

Many threatened bryophytes are restricted to patchy and temporary substrates such as dead wood and tree stems. Their persistence depends on successful colonizations of new patches. Spore germination may then be limited by substrate quality and wetness.

In vitro experiments were used to test the effects of pH and moisture on the establishment of spores of the moss species Neckera pennata Hedw. and Buxbaumia viridis (DC) Moug. & Nestl.

Low pH and water potential prolonged the lag phase preceding germination and reduced final germination. The interaction between pH and moisture suggests that high water availability facilitates germination at suboptimal pH, and vice versa.

The results reflect the species’ habitats: the wood‐inhabiting B. viridis had higher capacity to germinate at low pH, while spores of the epiphyte N. pennata showed earlier germination at low water potential and survived longer in a dry state. This supports the notion that bryophytes are most strongly affected by substrate quality during establishment.

We suggest that a trade‐off exists among moss spores between the ability to colonize substrates with low moisture‐holding capacity and low pH, and that the positive effect of high pH is largely that it speeds up germination thereby enabling the spores to exploit short, moist periods.
A preclinical pharmacokinetic/pharmacodynamic approach to determine a dose of GnRH, for treatment of ovarian follicular cyst in cattle
Authors: MONNOYER S. , GUYONNET J. , TOUTAIN P. L.
Published: December 2004

The objective of this study was to explore the value of a preclinical PK/PD approach to determine a gonadotropin‐releasing hormone (GnRH) dose in cows using the pituitary LH response as a surrogate endpoint.

Using an indirect effect model with stimulation of the LH entry rate, the in vivo basic pharmacodynamic parameters of GnRH were determined. The EC50 of GnRH was 51 ± 16 pg/mL, the EC50 being the GnRH plasma concentration able to produce 50% of the maximum possible stimulation (Smax) of the hypophysis (Smax = 48 ± 13). From individual PK/PD parameters, the ED50 of GnRH, i.e. the estimated dose of GnRH required to determine half the maximum possible stimulating effect on LH release, was calculated to 62 μg/h per cow. Using the PK/PD model, the GnRH dose required to achieve a selected breakpoint value of 5 ng/mL for maximum LH concentration (surrogate value for LH concentration predicting clinical efficacy for cystic conditions), was 52 ± 18 μg and for a standard GnRH dose of 100 μg, the mean maximum plasma LH concentration predicted by the model was 7.22 ± 0.98 ng/mL.
Max Weber
Authors: Peukert Helge
Published: December 2004

Abstract.  This paper argues that Weber's outline and research program is only of limited relevance for present‐day economic sociology and heterodox economics because Weber had a rather narrow and static understanding of rationality and the economy. Uncertainty, both as a basic fact of economic life and in the interpretation of what rational action means in specific contexts, is missing in his approach. After a short discussion of the secondary literature on Weber's methodology, the paper focuses on the most important writings of Weber on methods and economics (e.g., his outline and some parts of Economy and Society). The result of our investigation is that Weber shared a rather narrow, neoclassical understanding of the Austrian variant of economics. His important construction of goal‐oriented behavior as the major methodological advice to analyze human action presupposes the idealized assumptions of perfect knowledge. His understanding of the market exchange process, price setting, and the functioning of full competition are rather conventional and elementary. Weber's genius did not materialize in the field of economics, but in his sociology of religion and law and in his sociology of domination.
Increasing the Role of Environmental Taxes and Charges as a Policy Instrument in Developing Countries
Authors: Backhaus Juergen G.
Published: December 2004

Abstract.  The judicious use of natural resources is a crucial prerequisite for sustainable growth not just in developed countries but even more so in the third world. More generally, natural resource use is determined to a substantial degree by the tax structure governing a country's economic activity. When a tax constitution can be designed that stimulates the judicious use of natural resources, an important step toward achieving sustainable growth has been made. Designing such a constitution is not a simple task, however. For third‐world countries, the task is further complicated by at least three factors. First, the tax system has to be exceedingly simple, since both number and quality of tax instruments available to third‐world governments tend to be limited. Second, the legal system tends to mirror the state of economic development. This limits not only the tax structure an economy can bear; it also limits a government's ability to regulate natural resource use by legal means. Third, the more elaborate a legal system, the more diversity it affords its country for economic activity, including opportunities for the division of labor, that is, international competition and trade.
Echoes of Henry George in Modern Analysis
Authors: Holcombe Randall G.
Published: December 2004

Abstract.  These comments were prepared in response to the session “Echoes of Henry George in Modern Analysis” presented at the 2002 meetings of the Southern Economic Association. Professor Holcombe prepared his comments at this journal's request at a later time.
Social Networks and Business Success
Authors: Kristiansen Stein
Published: December 2004

Abstract.  The main objective of this paper is to illuminate social and cultural preconditions for networking and success in business in an African context. By in‐depth studies of small‐scale entrepreneurs in the wood business in Tanzania, we find that people belonging to an Asian subculture probably have a better standing for entering and thriving in business, due to group cohesion, mobility, and level of education. Through high‐quality social networks, characterized by a high number and variety of relations, certain groups seem to be in a better position to enact their business environment and raise entrepreneurial resources such as motivation and ideas, information, capital, and trust. To reduce social discontent and inter‐ethnic and religious conflicts in this area, we suggest that policy measures be taken to enhance levels of education and access to information for all citizens to create a “level playing field” in economic affairs.
Enhancing Chinese tone recognition by manipulating amplitude envelope: Implications for cochlear implants
Authors: Luo Xin , Fu Qian-Jie
Published: December 2004

Tone recognition is important for speech understanding in tonal languages such as Mandarin Chinese. Cochlear implant patients are able to perceive some tonal information by using temporal cues such as periodicity-related amplitude fluctuations and similarities between the fundamental frequency (F0) contour and the amplitude envelope. The present study investigates whether modifying the amplitude envelope to better resemble the F0 contour can further improve tone recognition in multichannel cochlear implants. Chinese tone and vowel recognition were measured for six native Chinese normal-hearing subjects listening to a simulation of a four-channel cochlear implant speech processor with and without amplitude envelope enhancement. Two algorithms were proposed to modify the amplitude envelope to more closely resemble the F0 contour. In the first algorithm, the amplitude envelope as well as the modulation depth of periodicity fluctuations was adjusted for each spectral channel. In the second algorithm, the overall amplitude envelope was adjusted before multichannel speech processing, thus reducing any local distortions to the speech spectral envelope. The results showed that both algorithms significantly improved Chinese tone recognition. By adjusting the overall amplitude envelope to match the F0 contour before multichannel processing, vowel recognition was better preserved and less speech-processing computation was required. The results suggest that modifying the amplitude envelope to more closely resemble the F0 contour may be a useful approach toward improving Chinese-speaking cochlear implant patients’ tone recognition.
Geographic variations in the whistles of spinner dolphins (Stenella longirostris) of the Main Hawai‵ian Islands
Authors: Bazúa-Durán Carmen , Au Whitlow W. L.
Published: December 2004

Geographic variations in the whistles of Hawai‵ian spinner dolphins are discussed by comparing 27 spinner dolphin pods recorded in waters off the Islands of Kaua‵i, O‵ahu, Lāna‵i, and Hawai‵i. Three different behavioral states, the number of dolphins observed in each pod, and ten parameters extracted from each whistle contour were considered by using clustering and discriminant function analyses. The results suggest that spinner dolphin pods in the Main Hawai‵ian Islands share characteristics in approximately 48% of their whistles. Spinner dolphin pods had similar whistle parameters regardless of the island, location, and date when they were sampled and the dolphins’ behavioral state and pod size. The term ‵‵whistle-specific subgroup” (WSS) was used to designate whistle groups with similar whistles parameters (which could have been produced in part by the same dolphins). The emission rate of whistles was higher when spinner dolphins were socializing than when they were traveling or resting, suggesting that whistles are mainly used during close-range interactions. Spinner dolphins also seem to vary whistle duration according to their general behavioral state. Whistle duration and the number of turns and steps of a whistle may be more important in delivering information at the individual level than whistle frequency parameters.
Robust and accurate fundamental frequency estimation based on dominant harmonic components
Authors: Nakatani Tomohiro , Irino Toshio
Published: December 2004

This paper presents a new method for robust and accurate fundamental frequency (F0) estimation in the presence of background noise and spectral distortion. Degree of dominance and dominance spectrum are defined based on instantaneous frequencies. The degree of dominance allows one to evaluate the magnitude of individual harmonic components of the speech signals relative to background noise while reducing the influence of spectral distortion. The fundamental frequency is more accurately estimated from reliable harmonic components which are easy to select given the dominance spectra. Experiments are performed using white and babble background noise with and without spectral distortion as produced by a SRAEN filter. The results show that the present method is better than previously reported methods in terms of both gross and fine F0 errors.
Human temporal auditory acuity as assessed by envelope following responses
Authors: Purcell David W. , John Sasha M. , Schneider Bruce A. , Picton Terence W.
Published: December 2004

Temporal auditory acuity, the ability to discriminate rapid changes in the envelope of a sound, is essential for speech comprehension. Human envelope following responses (EFRs) recorded from scalp electrodes were evaluated as an objective measurement of temporal processing in the auditory nervous system. The temporal auditory acuity of older and younger participants was measured behaviorally using both gap and modulation detection tasks. These findings were then related to EFRs evoked by white noise that was amplitude modulated (25% modulation depth) with a sweep of modulation frequencies from 20 to 600 Hz. The frequency at which the EFR was no longer detectable was significantly correlated with behavioral measurements of gap detection (r=−0.43), and with the maximum perceptible modulation frequency (r=0.72). The EFR techniques investigated here might be developed into a clinically useful objective estimate of temporal auditory acuity for subjects who cannot provide reliable behavioral responses.
Noise emission during the first powerboat race in an Alpine lake and potential impact on fish communities
Authors: Amoser Sonja , Wysocki Lidia Eva , Ladich Friedrich
Published: December 2004

In order to assess the effects of high-speed boating on fish communities, noise levels were measured during the first Class 1 powerboat race on the Austrian Lake Traunsee. The noise spectra were compared to natural ambient noise and hearing abilities of four native fish species. Sound pressure levels (SPLs) were significantly elevated during the training heats and the race compared with natural levels, reaching up to 128 dB re 1 μPa (instantaneous SPL) at a distance of 300 m to the powerboats. Continuous equivalent SPLs were significantly lower during training and the pole position race compared to the race itself because fewer boats were simultaneously on the lake. The hearing abilities of the native hearing specialists and generalists were investigated. While carp and roach (two cyprinids) showed enhanced auditory sensitivity typical for hearing specialists, perch and whitefish were much less sensitive to sounds. Comparisons between power boat noise spectra and audiograms showed that the cyprinids can detect the boats up to several hundred meters distance because the main noise energy is well within the most sensitive hearing range. The hearing generalists, however, probably only perceive the first harmonic of the boat noise at close distances.
Methodological aspects of an adaptive multidirectional pattern search to optimize speech perception using three hearing-aid algorithms
Authors: Franck Bas A. M. , Dreschler Wouter A. , Lyzenga Johannes
Published: December 2004

In this study we investigated the reliability and convergence characteristics of an adaptive multidirectional pattern search procedure, relative to a nonadaptive multidirectional pattern search procedure. The procedure was designed to optimize three speech-processing strategies. These comprise noise reduction, spectral enhancement, and spectral lift. The search is based on a paired-comparison paradigm, in which subjects evaluated the listening comfort of speech-in-noise fragments. The procedural and nonprocedural factors that influence the reliability and convergence of the procedure are studied using various test conditions. The test conditions combine different tests, initial settings, background noise types, and step size configurations. Seven normal hearing subjects participated in this study. The results indicate that the reliability of the optimization strategy may benefit from the use of an adaptive step size. Decreasing the step size increases accuracy, while increasing the step size can be beneficial to create clear perceptual differences in the comparisons. The reliability also depends on starting point, stop criterion, step size constraints, background noise, algorithms used, as well as the presence of drifting cues and suboptimal settings. There appears to be a trade-off between reliability and convergence, i.e., when the step size is enlarged the reliability improves, but the convergence deteriorates.
Robustness of spatial average equalization: A statistical reverberation model approach
Authors: Bharitkar Sunil , Hilmes Philip , Kyriakakis Chris
Published: December 2004

Traditionally, multiple listener room equalization is performed to improve sound quality at all listeners, during audio playback, in a multiple listener environment (e.g., movie theaters, automobiles, etc.). A typical way of doing multiple listener equalization is through spatial averaging, where the room responses are averaged spatially between positions and an inverse equalization filter is found from the spatially averaged result. However, the equalization performance, will be affected if there is a mismatch between the position of the microphones (which are used for measuring the room responses for designing the equalization filter) and the actual center of listener head position (during playback). In this paper, we will present results on the effects of microphone-listener mismatch on spatial average equalization performance. The results indicate that, for the analyzed rectangular configuration, the region of effective equalization depends on (i) the distance of a listener from the source, (ii) the amount of mismatch between the responses, and (iii) the frequency of the audio signal. We also present some convergence analysis to interpret the results.
An echolocation model for the restoration of an acoustic image from a single-emission echo
Authors: Matsuo Ikuo , Yano Masafumi
Published: December 2004

Bats can form a fine acoustic image of an object using frequency-modulated echolocation sound. The acoustic image is an impulse response, known as a reflected-intensity distribution, which is composed of amplitude and phase spectra over a range of frequencies. However, bats detect only the amplitude spectrum due to the low-time resolution of their peripheral auditory system, and the frequency range of emission is restricted. It is therefore necessary to restore the acoustic image from limited information. The amplitude spectrum varies with the changes in the configuration of the reflected-intensity distribution, while the phase spectrum varies with the changes in its configuration and location. Here, by introducing some reasonable constraints, a method is proposed for restoring an acoustic image from the echo. The configuration is extrapolated from the amplitude spectrum of the restricted frequency range by using the continuity condition of the amplitude spectrum at the minimum frequency of the emission and the minimum phase condition. The determination of the location requires extracting the amplitude spectra, which vary with its location. For this purpose, the Gaussian chirplets with a carrier frequency compatible with bat emission sweep rates were used. The location is estimated from the temporal changes of the amplitude spectra.
The bat head-related transfer function reveals binaural cues for sound localization in azimuth and elevation
Authors: Aytekin Murat , Grassi Elena , Sahota Manjit , Moss Cynthia F.
Published: December 2004

Directional properties of the sound transformation at the ear of four intact echolocating bats, Eptesicus fuscus, were investigated via measurements of the head-related transfer function (HRTF). Contributions of external ear structures to directional features of the transfer functions were examined by remeasuring the HRTF in the absence of the pinna and tragus. The investigation mainly focused on the interactions between the spatial and the spectral features in the bat HRTF. The pinna provides gain and shapes these features over a large frequency band (20–90 kHz), and the tragus contributes gain and directionality at the high frequencies (60 to 90 kHz). Analysis of the spatial and spectral characteristics of the bat HRTF reveals that both interaural level differences (ILD) and monaural spectral features are subject to changes in sound source azimuth and elevation. Consequently, localization cues for horizontal and vertical components of the sound source location interact. Availability of multiple cues about sound source azimuth and elevation should enhance information to support reliable sound localization. These findings stress the importance of the acoustic information received at the two ears for sound localization of sonar target position in both azimuth and elevation.
Auditory processing of real and illusory changes in frequency modulation (FM) phase
Authors: Carlyon Robert P. , Micheyl Christophe , Deeks John M. , Moore Brian C. J.
Published: December 2004

Auditory processing of frequency modulation (FM) was explored. In experiment 1, detection of a π-radians modulator phase shift deteriorated as modulation rate increased from 2.5 to 20 Hz, for 1- and 6-kHz carriers. In experiment 2, listeners discriminated between two 1-kHz carriers, where, mid-way through, the 10-Hz frequency modulator had either a phase shift or increased in depth by ΔD% for half a modulator period. Discrimination was poorer for ΔD=4% than for smaller or larger increases. These results are consistent with instantaneous frequency being smoothed by a time window with a total duration of about 110 ms. In experiment 3, the central 200-ms of a 1-s 1-kHz carrier modulated at 5 Hz was replaced by noise, or by a faster FM applied to a more intense 1-kHz carrier. Listeners heard the 5-Hz FM continue at the same depth throughout the stimulus. Experiments 4 and 5 showed that, after an FM tone had been interrupted by a 200-ms noise, listeners were insensitive to the phase at which the FM resumed. It is argued that the auditory system explicitly encodes the presence, and possibly the rate and depth, of FM in a way that does not preserve information on FM phase.
Vocal tract filtering and the “coo” of doves
Authors: Fletcher Neville H. , Riede Tobias , Beckers Gabriël J. L. , Suthers Roderick A.
Published: December 2004

Ring doves (Streptopelia risoria) produce a “coo” vocalization that is essentially a pure-tone sound at a frequency of about 600 Hz and with a duration of about 1.5 s. While making this vocalization, the dove inflates the upper part of its esophagus to form a thin-walled sac structure that radiates sound to the surroundings. It is a reasonable assumption that the combined influence of the trachea, glottis and inflated upper esophagus acts as an effective band-pass filter to eliminate higher harmonics generated by the vibrating syringeal valve. Calculations reported here indicate that this is indeed the case. The tracheal tube, terminated by a glottal constriction, is the initial resonant structure, and subsequent resonant filtering takes place through the action of the inflated esophageal sac. The inflated esophagus proves to be a more efficient sound radiating mechanism than an open beak. The action of this sac is only moderately affected by the degree of inflation, although an uninflated esophagus is inactive as a sound radiator. These conclusions are supported by measurements and observations that have been reported in a companion paper.
Distortion product otoacoustic emissions provide clues to hearing mechanisms in the frog ear
Authors: Vassilakis Pantelis N. , Meenderink Sebastiaan W. F. , Narins Peter M.
Published: December 2004

2 f 1 -f 2 and 2 f2-f1 distortion product otoacoustic emissions (DPOAEs) were recorded from both ears of male and female Rana pipiens pipiens and Rana catesbeiana. The input-output (I/O) curves obtained from the amphibian papilla (AP) of both frog species are analogous to I/O curves recorded from mammals suggesting that, similarly to the mammalian cochlea, there may be an amplification process present in the frog AP. DPOAE level dependence on L1-L2 is different from that in mammals and consistent with intermodulation distortion expectations. Therefore, if a mechanical structure in the frog inner ear is functioning analogously to the mammalian basilar membrane, it must be more broadly tuned. DPOAE audiograms were obtained for primary frequencies spanning the animals’ hearing range and selected stimulus levels. The results confirm that DPOAEs are produced in both papillae, with R. catesbeiana producing stronger emissions than R. p. pipiens. Consistent with previously reported sexual dimorphism in the mammalian and anuran auditory systems, females of both species produce stronger emissions than males. Moreover, it appears that 2 f1-f2 in the frog is generated primarily at the DPOAE frequency place, while 2 f2-f1 is generated primarily at a frequency place around the primaries. Regardless of generation place, both emissions within the AP may be subject to the same filtering mechanism, possibly the tectorial membrane.
Development of a laser photothermoacoustic frequency-swept system for subsurface imaging: Theory and experiment
Authors: Fan Ying , Mandelis Andreas , Spirou Gloria , Alex Vitkin I.
Published: December 2004

In conventional biomedical photoacoustic imaging systems, a pulsed laser is used to generate time-of-flight acoustic information of the subsurface features. This paper reports the theoretical and experimental development of a new frequency-domain (FD) photo-thermo-acoustic (PTA) principle featuring frequency sweep (chirp) and heterodyne modulation and lock-in detection of a continuous-wave laser source at 1064 nm wavelength. PTA imaging is a promising new technique which is being developed to detect tumor masses in turbid biological tissue. Owing to the linear relationship between the depth of acoustic signal generation and the delay time of signal arrival to the transducer, information specific to a particular depth can be associated with a particular frequency in the chirp signal. Scanning laser modulation with a linear frequency sweep method preserves the depth-to-delay time linearity and recovers FD-PTA signals from a range of depths. Preliminary results performed on rubber samples and solid tissue phantoms indicate that the FD-PTA technique has the potential to be a reliable tool for biomedical depth-profilometric imaging.
Analysis and modeling of broadband airgun data influenced by nonlinear internal waves
Authors: Frank Scott D. , Badiey Mohsen , Lynch James F. , Siegmann William L.
Published: December 2004

To investigate acoustic effects of nonlinear internal waves, the two southwest tracks of the SWARM 95 experiment are considered. An airgun source produced broadband acoustic signals while a packet of large nonlinear internal waves passed between the source and two vertical linear arrays. The broadband data and its frequency range (10–180 Hz) distinguish this study from previous work. Models are developed for the internal wave environment, the geoacoustic parameters, and the airgun source signature. Parabolic equation simulations demonstrate that observed variations in intensity and wavelet time–frequency plots can be attributed to nonlinear internal waves. Empirical tests are provided of the internal wave-acoustic resonance condition that is the apparent theoretical mechanism responsible for the variations. Peaks of the effective internal wave spectrum are shown to coincide with differences in dominant acoustic wavenumbers comprising the airgun signal. The robustness of these relationships is investigated by simulations for a variety of geoacoustic and nonlinear internal wave model parameters.
Sound equalization in a large region of a rectangular enclosure (L)
Authors: Sarris John C. , Jacobsen Finn , Cambourakis George E.
Published: December 2004

The work presented by Santillán [J. Acoust. Soc. Am. 110, 1989–1997 (2001)] about equalization at low frequencies in rectangular enclosures is extended, and topics that remained unaddressed in the original study are treated in this paper. A modification is introduced to the original cost function that leads to a least-squares problem formulation that demonstrates increased robustness, and the multiple-error LMS (Least Mean Square) adaptive algorithm is employed to approximate the coefficients of the equalization filters to their optimum values. Other issues studied in this paper include the dependence of the limits of the zone of equalization on factors such as the damping constant of the modes of the enclosure, the number of sources, and the driving frequency.
Wave interaction in acoustic resonators with and without hysteresis
Authors: Ostrovsky Lev A.
Published: December 2004

Nonlinear interaction of counterpropagating waves in solids is considered by using a general approach taking into account only the cumulative (resonant) nonlinear perturbations giving a nonzero contribution over the period and, consecutively, potentially able to significantly modify the linear solution. Different stress-strain relations are addressed, including those with hysteresis which serve as basic models for the recent acoustic experiments with rock and metals. An important case of the interaction of counterpropagating waves with close amplitudes in a high-Q resonator (bar) with hysteresis is specially addressed and compared with the case of a ring resonator.
Deletion of the Dynein Heavy-Chain Gene
DYN1
Leads to Aberrant Nuclear Positioning and Defective Hyphal Development in
Candida albicans
Authors: Martin R. , Walther A. , Wendland J.
Published: December 2004

Cytoplasmic dynein is a microtubule-associated minus-end-directed motor protein.
CaDYN1
encodes the single dynein heavy-chain gene of
Candida albicans
. The open reading frames of both alleles of
CaDYN1
were completely deleted via a PCR-based approach.
Cadyn1
mutants are viable but grow more slowly than the wild type. In vivo time-lapse microscopy was used to compare growth of wild-type (SC5314) and
dyn1
mutant strains during yeast growth and after hyphal induction. During yeast-like growth,
Cadyn1
strains formed chains of cells. Chromosomal
TUB1
-
GFP
and
HHF1
-
GFP
alleles were used both in wild-type and mutant strains to monitor the orientation of mitotic spindles and nuclear positioning in
C. albicans
. In vivo fluorescence time-lapse analyses with
HHF1-GFP
over several generations indicated defects in
dyn1
cells in the realignment of spindles with the mother-daughter axis of yeast cells compared to that of the wild type. Mitosis in the
dyn1
mutant, in contrast to that of wild-type yeast cells, was very frequently completed in the mother cells. Nevertheless, daughter nuclei were faithfully transported into the daughter cells, resulting in only a small number of multinucleate cells.
Cadyn1
mutant strains responded to hypha-inducing media containing
l
-proline or serum with initial germ tube formation. Elongation of the hyphal tubes eventually came to a halt, and these tubes showed a defect in the tipward localization of nuclei. Using a heterozygous
DYN1/dyn1
strain in which the remaining copy was controlled by the regulatable
MAL2
promoter, we could switch between wild-type and mutant phenotypes depending on the carbon source, indicating that the observed mutant phenotypes were solely due to deletion of
DYN1
.
Relaxed Primer Specificity Associated with Reverse Transcriptases Encoded by the pFOXC Retroplasmids of
Fusarium oxysporum
Authors: Simpson E. Barry , Ross Shannon L. , Marchetti Sarah E. , Kennell John C.
Published: December 2004

The pFOXC mitochondrial retroplasmids are small, autonomously replicating linear DNAs that have a telomere-like repeat of a 5-bp sequence at their termini. The plasmids are possible evolutionary precursors of the ribonucleoprotein complex telomerase, as they encode an active reverse transcriptase (RT) that is involved in plasmid replication. Using an in vitro system to study reverse transcription, we show that the pFOXC RT is capable of copying in vitro-synthesized RNAs by use of cDNA primers or extension of snapped-back RNA templates. The ability of the pFOXC RT to use base-paired primers distinguishes it from the closely related RTs encoded by the Mauriceville and Varkud mitochondrial retroplasmids of
Neurospora
spp. Reaction products are similar, but not identical, to those obtained with conventional RTs, and differences reflect the ability of the pFOXC RT to initiate cDNA synthesis with loosely associated primers. The pFOXC RT can also copy DNA templates and extend 3′ mismatched DNA oligonucleotide primers. Analysis of pFOXC in vivo replication intermediates suggests that telomeric repeats are added during reverse transcription, and the ability to extend loosely associated primers could play a role in repeat formation by mechanisms similar to those associated with telomerase and certain non-long-terminal-repeat retrotransposons.
Snf7p, a Component of the ESCRT-III Protein Complex, Is an Upstream Member of the
RIM101
Pathway in
Candida albicans
Authors: Kullas Amy L. , Li Mingchun , Davis Dana A.
Published: December 2004

The success of
Candida albicans
as an opportunistic pathogen is based in part on its ability to adapt to diverse environments. The
RIM101
pathway governs adaptation to neutral-alkaline environments and is required for virulence. Analysis of a genomic two-hybrid study conducted with
Saccharomyces cerevisiae
revealed that components involved in multivesicular bodies (MVB) transport may interact with
RIM101
pathway members. Thus, we hypothesized that these proteins may function in the
RIM101
pathway in
C. albicans
. We identified
C. albicans
homologs to
S. cerevisiae
Snf7p, Vps4p, and Bro1p and generated mutants in the cognate gene. We found that
snf7
Δ/Δ mutants, but not
vps4
Δ/Δ nor
bro1
Δ/Δ mutants, had phenotypes similar to, but more severe than, those of
RIM101
pathway mutants. We found that the constitutively active
RIM101-405
allele partially rescued
snf7
Δ/Δ mutant phenotypes. The
vps4
Δ/Δ mutant had subtle phenotypes, but these were not rescued by the
RIM101-405
allele. Further, we found that the
snf7
Δ/Δ,
vps4
Δ/Δ, and
bro1
Δ/Δ mutants did not efficiently localize the vital dye FM4-64 to the vacuole and that it was often accumulated in an MVB-like compartment. This phenotype was not rescued by
RIM101-405
or observed in
RIM101
pathway mutants. These results suggest that Snf7p may serve two functions in the cell: one as a
RIM101
pathway member and one for MVB transport to the vacuole.
Control of rRNA Synthesis in
Escherichia coli
: a Systems Biology Approach
Authors: Dennis Patrick P. , Ehrenberg Mans , Bremer Hans
Published: December 2004

The first part of this review contains an overview of the various
contributions and models relating to the control of rRNA synthesis
reported over the last 45 years. The second part describes a systems
biology approach to identify the factors and effectors that control the
interactions between RNA polymerase and rRNA (
rrn
) promoters
of
Escherichia coli
bacteria during exponential growth in
different media. This analysis is based on measurements of absolute
rrn
promoter activities as transcripts per minute per promoter
in bacterial strains either deficient or proficient in the synthesis of
the factor Fis and/or the effector ppGpp. These absolute promoter
activities are evaluated in terms of
rrn
promoter strength
(
V
max
/

K
m

) and free RNA
polymerase concentrations. Three major conclusions emerge from this
evaluation. First, the
rrn
promoters are not saturated with
RNA polymerase. As a consequence, changes in the concentration of free
RNA polymerase contribute to changes in
rrn
promoter
activities. Second,
rrn
P2 promoter strength is not
specifically regulated during exponential growth at different rates;
its activity changes only when the concentration of free RNA polymerase
changes. Third, the effector ppGpp reduces the strength of the
rrn
P1 promoter both directly and indirectly by reducing
synthesis of the stimulating factor Fis. This control of
rrn
P1 promoter strength forms part of a larger feedback loop that adjusts
the synthesis of ribosomes to the availability of amino acids via amino
acid-dependent control of ppGpp
accumulation.
Metagenomics: Application of Genomics to Uncultured Microorganisms
Authors: Handelsman Jo
Published: December 2004

Metagenomics (also referred to as environmental and community genomics) is the genomic analysis of microorganisms by direct extraction and cloning of DNA from an assemblage of microorganisms. The development of metagenomics stemmed from the ineluctable evidence that as-yet-uncultured microorganisms represent the vast majority of organisms in most environments on earth. This evidence was derived from analyses of 16S rRNA gene sequences amplified directly from the environment, an approach that avoided the bias imposed by culturing and led to the discovery of vast new lineages of microbial life. Although the portrait of the microbial world was revolutionized by analysis of 16S rRNA genes, such studies yielded only a phylogenetic description of community membership, providing little insight into the genetics, physiology, and biochemistry of the members. Metagenomics provides a second tier of technical innovation that facilitates study of the physiology and ecology of environmental microorganisms. Novel genes and gene products discovered through metagenomics include the first bacteriorhodopsin of bacterial origin; novel small molecules with antimicrobial activity; and new members of families of known proteins, such as an Na
+
(Li
+
)/H
+
antiporter, RecA, DNA polymerase, and antibiotic resistance determinants. Reassembly of multiple genomes has provided insight into energy and nutrient cycling within the community, genome structure, gene function, population genetics and microheterogeneity, and lateral gene transfer among members of an uncultured community. The application of metagenomic sequence information will facilitate the design of better culturing strategies to link genomic analysis with pure culture studies.
Metabolic Interdependence of Obligate Intracellular Bacteria and Their Insect Hosts
Authors: Zientz Evelyn , Dandekar Thomas , Gross Roy
Published: December 2004

Mutualistic associations of obligate intracellular bacteria and insects have attracted much interest in the past few years due to the evolutionary consequences for their genome structure. However, much less attention has been paid to the metabolic ramifications for these endosymbiotic microorganisms, which have to compete with but also to adapt to another metabolism—that of the host cell. This review attempts to provide insights into the complex physiological interactions and the evolution of metabolic pathways of several mutualistic bacteria of aphids, ants, and tsetse flies and their insect hosts.
VACANCY FORMATION IN CoSi2 AND NiSi2 FROM AB INITIO CALCULATION
Authors: WANG T. , DAI Y.-B. , OUYANG S.-K. , WANG Q.-K. , SHEN H.-S. , WU J.-S.
Published: December 2004

The lattice structure and electronic properties of perfect and defective CoSi 2 and NiSi 2 have been calculated using an ab initio plane-wave ultrasoft pseudopotential method based on the generalized gradient approximations (GGA). Special attention is paid to the formation energies of the vacancies, which largely depend on the atomic chemical potentials of Si and metal atom: in Si -rich limit, the formation energies of Si and Co vacancies are 2.39 eV and 0.56 eV whilst those are 1.53 eV and 2.29 eV in Co -rich limit in CoSi 2, respectively. For NiSi 2, the formation energies of Si and Ni vacancies are 0.56 eV and 1.25 eV in Si -rich limit and those are 0.04 eV and 2.3 eV in Ni -rich limit.
FLOQUET FORMALISM OF QUANTUM PUMPS
Authors: KIM SANG WOOK
Published: December 2004

We review Floquet formalism of quantum electron pumps. In the Floquet formalism the quantum pump is regarded as a time dependent scattering system, which allows us to go beyond the adiabatic limit. It can be shown that the well-known adiabatic formula given by Brouwer can be derived from the adiabatic limit of Floquet formalism. We compare various physical properties of the quantum pump both in the adiabatic and in the non-adiabatic regime using the Floquet theory.
BPR AND CHANGE MANAGEMENT: A CASE STUDY OF A LARGE SPANISH ELECTRICITY COMPANY
Authors: ALBIZU ENEKA , OLAZARAN MIKEL , SIMON KATRIN
Published: December 2004

The aim of this study is to explain the key factors affecting the success of BPR in a large European electricity company. First a review of the "business process re-engineering" (BPR) concept and its relationship with organisational change and change management is carried out. This is followed by the analysis of the idea of BPR adopted by the company, an explanation of the main guidelines of the implementation carried out, and an interpretation of the results that were obtained. The balance, both in economic and change management terms, was highly positive, although organisational and cultural change, in a strong sense of the term, remains a matter still to be resolved by the company.
THE EFFECT OF INDUSTRY CLOCKSPEED ON MAKE-BUY DECISIONS IN THE FACE OF RADICAL INNOVATIONS: AN EMPIRICAL TEST
Authors: PERRONS ROBERT K. , RICHARDS MATTHEW G. , PLATTS KEN
Published: December 2004

Evidence from management and business strategy research is divided over whether or not a firm should outsource the components and processes underpinning a new and potentially radical innovation. This investigation introduces ideas and evidence from the areas of supplier relations and industry clockspeed, and attempts to reconcile conflicting conclusions from earlier research by using a survey to measure supply chain management practices from a broad range of manufacturers in the UK. The results show that an industry's clockspeed has no significant bearing on the success or failure of any particular make-buy strategy for a radical innovation. The findings also indicate that maintaining strong ties with suppliers yields no significant long-term benefit for firms contending with radical new technologies.
Upregulation of hepatic LDL receptor-related protein in nephrotic syndrome: response to statin therapy
Authors: Kim Sara , Kim Choong H. , Vaziri Nosratola D.
Published: December 2004

Nephrotic syndrome (N-S) is associated with elevated plasma concentration and impaired clearance of VLDL, chylomicrons (CM), and their atherogenic remnants. These abnormalities are largely due to lipoprotein lipase, hepatic triglyceride lipase, and VLDL receptor deficiencies and impaired HDL-mediated shuttling of apoE and apoC between the nascent and remnant VLDL and CM. LRP is a multifaceted endocytic receptor that is heavily expressed in the liver. LRP recognizes at least 30 different ligands including VLDL and CM remnants. These observations prompted the present study to discern the effect of N-S on hepatic LRP gene and protein expressions. The study further sought to explore the effect of lipid-lowering therapy on LRP expression in N-S. Sprague-Dawley rats were randomized to the N-S (given ip injections of puromycin aminonucleoside; 130 mg/kg on day 1, 60 mg/kg on day 14) and placebo-injected control groups. On day 14, animals were subdivided into statin-treated (rosuvastatin; 20 mg·kg−1·day−1mixed with powdered chow) and untreated groups and studied on day 28. The untreated N-S group exhibited severe proteinuria, hypoalbuminemia, hypercholesterolemia, hypertriglyceridemia, and marked elevation of hepatic tissue LRP mRNA and protein abundance. Statin administration for 2 wk resulted in significant improvements of plasma lipid profile, proteinuria, and hypoalbuminemia as well as hepatic LRP mRNA and protein abundance. In contrast, statin administration had no significant effect on either plasma lipids or hepatic LRP levels in the normal control rats. In conclusion, N-S results in marked upregulation of hepatic LRP expression that is partly reversed with statin administration. These findings exclude depressed hepatic LRP expression as the primary cause of elevated plasma lipoprotein remnants in N-S.
Fetal cerebrovascular acclimatization responses to high-altitude, long-term hypoxia: a model for prenatal programming of adult disease?
Authors: Longo Lawrence D. , Pearce William J.
Published: December 2004

During the past several decades, many risk factors for cerebrovascular and cardiovascular disease have been identified. More recently, it has been appreciated that inadequate nutrition and/or other intrauterine factors during fetal development may play an important role in the genesis of these conditions. An additional stress factor that may “program” the fetus for disease later in life is chronic hypoxia. In studies originally designed to examine the function of developing cerebral arterial function in response to long-term hypoxia (LTH), it has become clear that many cellular and subcellular changes may have important implications for later life. Here we review some of the significant alterations in fetal cerebral artery structure and function induced by high-altitude (3,820 m, 12,470 ft) LTH (∼110 days). LTH is associated with augmentation or upregulation of presynaptic functions, including responses to perivascular (i.e., sympathetic) nerve stimulation, and structural maturational changes. In contrast, many postsynaptic functions related to the Ca2+-dependent contractile pathway tend to be downregulated, whereas elements of the Ca2+-independent contraction pathway are upregulated. The results emphasize the role of high-altitude LTH in modulating many aspects of electromechanical and pharmacomechanical coupling in the developing cerebral vasculature. A complicating factor is that the regulation of cerebrovascular tone by Ca2+-dependent and Ca2+-independent pathways changes significantly as a function of maturational age. In addition to highlighting independent regulation of various elements of the signal transduction cascade, the studies demonstrate the potential for LTH to program the fetus for cerebrovascular and other disease as an adult.