bluuebunny/crossref_metadata_2025 huggingface dataset:
Low frequency wind noise contributions in measurement microphones
Authors: Raspet Richard , Yu Jiao , Webster Jeremy
Published: March 2008

In a previous paper [R. Raspet, et al., J. Acoust. Soc. Am. 119, 834–843 (2006)], a method was introduced to predict upper and lower bounds for wind noise measured in spherical wind-screens from the measured incident velocity spectra. That paper was restricted in that the predictions were only valid within the inertial range of the incident turbulence, and the data were from a measurement not specifically designed to test the predictions. This paper extends the previous predictions into the source region of the atmospheric wind turbulence, and compares the predictions to measurements made with a large range of wind-screen sizes. Predictions for the turbulence–turbulence interaction pressure spectrum as well as the stagnation pressure fluctuation spectrum are calculated from a form fit to the velocity fluctuation spectrum. While the predictions for turbulence–turbulence interaction agree well with measurements made within large (1.0m) wind-screens, and the stagnation pressure predictions agree well with unscreened gridded microphone measurements, the mean shear–turbulence interaction spectra do not consistently appear in measurements.
Fast wave ultrasonic propagation in trabecular bone: Numerical study of the influence of porosity and structural anisotropy
Authors: Haïat G. , Padilla F. , Peyrin F. , Laugier P.
Published: March 2008

Our goal is to assess the potential of computational methods as an alternative to analytical models to predict the two longitudinal wave modes observed in cancellous bone and predicted by the Biot theory. A three-dimensional (3D) finite-difference time-domain method is coupled with 34 human femoral trabecular microstructures measured using microcomputed tomography. The main trabecular alignment (MTA) and the degree of anisotropy (DA) were assessed for all samples. DA values were comprised between 1.02 and 1.9. The influence of bone volume fraction (BV/TV) between 5% and 25% on the properties of the fast and slow waves was studied using a dedicated image processing algorithm to modify the initial 3D microstructures. A heuristic method was devised to determine when both wave modes are time separated. The simulations (performed in three perpendicular directions) predicted that both waves generally overlap in time for a direction of propagation perpendicular to the MTA. When these directions are parallel, both waves are separated in time for samples with high DA and BV/TV values. A relationship was found between the least bone volume fraction required for the observation of nonoverlapping waves and the degree of anisotropy: The higher the DA, the lower the least BV/TV.
Investigation of a glottal related harmonics-to-noise ratio and spectral tilt as indicators of glottal noise in synthesized and human voice signals
Authors: Murphy Peter J. , McGuigan Kevin G. , Walsh Michael , Colreavy Michael
Published: March 2008

The harmonics-to-noise ratio (HNR) of the voiced speech signal has implicitly been used to infer information regarding the turbulent noise level at the glottis. However, two problems exist for inferring glottal noise attributes from the HNR of the speech wave form: (i) the measure is fundamental frequency (f0) dependent for equal levels of glottal noise, and (ii) any deviation from signal periodicity affects the ratio, not just turbulent noise. An alternative harmonics-to-noise ratio formulation [glottal related HNR (GHNR’)] is proposed to overcome the former problem. In GHNR’ a mean over the spectral range of interest of the HNRs at specific harmonic/between-harmonic frequencies (expressed in linear scale) is calculated. For the latter issue [(ii)] two spectral tilt measures are shown, using synthesis data, to be sensitive to glottal noise while at the same time being comparatively insensitive to other glottal aperiodicities. The theoretical development predicts that the spectral tilt measures reduce as noise levels increase. A conventional HNR estimator, GHNR’ and two spectral tilt measures are applied to a data set of 13 pathological and 12 normal voice samples. One of the tilt measures and GHNR’ are shown to provide statistically significant differentiating power over a conventional HNR estimator.
Predicted attenuation of sound in a rigid-porous ground from an airborne source
Authors: Li Kai Ming
Published: March 2008

An approximate analytical formula has been derived for the prediction of sound fields in a semi-infinite rigid-porous ground due to an airborne source. The method starts by expressing the sound fields in an integral form, which can subsequently be evaluated by the method of steepest descents. The concept of effective impedance has been introduced by using a physically plausible assumption. The integral can then be simplified and evaluated analytically. The analytical solution can be expressed in a closed form analogous to the classical Weyl–Van der Pol formula that has been used for predicting sound fields above a rigid-porous ground. Extensive comparisons with the wave-based numerical solutions according to the fast field formulation and the direct evaluation of the integral have been conducted. It has been demonstrated that the analytical formula is sufficiently accurate to predict the penetration of sound into a wide range of outdoor ground surfaces.
Comparison between otoacoustic and auditory brainstem response latencies supports slow backward propagation of otoacoustic emissions
Authors: Moleti Arturo , Sisto Renata
Published: March 2008

Experimental measurements of the latency of transient evoked otoacoustic emission and auditory brainstem responses are compared, to discriminate between different cochlear models for the backward acoustic propagation of otoacoustic emissions. In most transmission-line cochlear models otoacoustic emissions propagate towards the base as a slow transverse traveling wave, whereas other models assume fast backward propagation via longitudinal compression waves in the fluid. Recently, sensitive measurements of the basilar membrane motion have cast serious doubts on the existence of slow backward traveling waves associated with distortion product otoacoustic emissions [He et al., Hear. Res. 228, 112–122 (2007)]. On the other hand, recent analyses of “Allen–Fahey” experiments suggest instead that the slow mechanism transports most of the otoacoustic energy [Shera et al., J. Acoust. Soc. Am. 122, 1564–1575 (2007)]. The two models can also be discriminated by comparing accurate estimates of the otoacoustic emission latency and of the auditory brainstem response latency. In this study, this comparison is done using human data, partly original, and partly from the literature. The results are inconsistent with fast otoacoustic propagation, and suggest that slow traveling waves on the basilar membrane are indeed the main mechanism for the backward propagation of the otoacoustic energy.
Acoustic model adaptation for ortolan bunting (Emberiza hortulana L.) song-type classification
Authors: Tao Jidong , Johnson Michael T. , Osiejuk Tomasz S.
Published: March 2008

Automatic systems for vocalization classification often require fairly large amounts of data on which to train models. However, animal vocalization data collection and transcription is a difficult and time-consuming task, so that it is expensive to create large data sets. One natural solution to this problem is the use of acoustic adaptation methods. Such methods, common in human speech recognition systems, create initial models trained on speaker independent data, then use small amounts of adaptation data to build individual-specific models. Since, as in human speech, individual vocal variability is a significant source of variation in bioacoustic data, acoustic model adaptation is naturally suited to classification in this domain as well. To demonstrate and evaluate the effectiveness of this approach, this paper presents the application of maximum likelihood linear regression adaptation to ortolan bunting (Emberiza hortulana L.) song-type classification. Classification accuracies for the adapted system are computed as a function of the amount of adaptation data and compared to caller-independent and caller-dependent systems. The experimental results indicate that given the same amount of data, supervised adaptation significantly outperforms both caller-independent and caller-dependent systems.
Mitochondrial DNA Content, an Inaccurate Biomarker of Mitochondrial Alteration in Human Immunodeficiency Virus-Related Lipodystrophy
Authors: Kim Min Ji , Jardel Claude , Barthélémy Cyrille , Jan Véronique , Bastard Jean Philippe , Fillaut-Chapin Sandrine , Houry Sydney , Capeau Jacqueline , Lombès Anne
Published: March 2008

Lipoatrophy is a prevalent side effect of antiretroviral treatment of human immunodeficiency virus (HIV) infection. Its mechanisms are still disputed but include mitochondrial toxicity and, in particular, mitochondrial DNA (mtDNA) depletion induced by nucleoside reverse transcriptase inhibitors. To obtain an integrated evaluation of the mitochondrial alteration in lipoatrophy, we investigated the DNA, RNA, and protein levels in 15 samples of abdominal subcutaneous adipose tissue from HIV-infected patients with peripheral lipoatrophy and compared the results with those for 15 samples from age- and body mass index-matched controls. The DNA and RNA analyses used PCR-based techniques, while proteins were quantified with enzyme-linked immunosorbent assay and measurement of activities with spectrophotometric assays. Depletion of mtDNA and mtDNA-encodedMT-CO2mRNA was present, but normal levels of mtDNA-dependent activity (cytochromecoxidase) and protein (MT-CO2p) showed that it was compensated for. An increase in nuclear-DNA-dependent mitochondrial activities (citrate synthase and malate dehydrogenase) and protein (COX4I1p), as well as transcriptional up-regulation of nuclear-DNA-encoded mitochondrial genes (COX4I1andUCP2), demonstrated increased mitochondrial biogenesis. However, the expression of the known transcription factors of mitochondrial biogenesis (TFAM,NRF1,GABPA,PPARGC1A,PPARGC1B, andPPRC1) was normal or decreased. Increased amounts of activated caspase 3 and ofDDIT3mRNA showed the induction of apoptosis and oxidative stress, respectively. The mtDNA content did not correlate with any other mitochondrial parameter. In conclusion, mtDNA content does not appear to be an accurate biomarker of mitochondrial alteration in lipoatrophic adipose tissue. The preservation of mtDNA-dependent mitochondrial functions occurred despite severe mtDNA depletion. The presence of significant oxidative stress and apoptosis did not correlate with the mtDNA content.
Activities of Daptomycin and Comparative Antimicrobials, Singly and in Combination, against Extracellular and Intracellular
Staphylococcus aureus
and Its Stable Small-Colony Variant in Human Monocyte-Derived Macrophages and in Broth
Authors: Baltch Aldona L. , Ritz William J. , Bopp Lawrence H. , Michelsen Phyllis , Smith Raymond P.
Published: March 2008

We investigated the antistaphylococcal activities of daptomycin, gentamicin, and rifampin against two
Staphylococcus aureus
strains and their stable small-colony variants, singly and in combination, in human monocyte-derived macrophages and in broth. Intracellularly, the three-drug combination and two-drug combinations with rifampin were most effective. Extracellularly, daptomycin, daptomycin plus gentamicin, gentamicin plus rifampin, and the three-drug combination had similar activities.
Intravaginal Immunization of Mice with Recombinant
Salmonella enterica
Serovar Typhimurium Expressing Human Papillomavirus Type 16 Antigens as a Potential Route of Vaccination against Cervical Cancer
Authors: Echchannaoui Hakim , Bianchi Matteo , Baud David , Bobst Martine , Stehle Jean-Christophe , Nardelli-Haefliger Denise
Published: March 2008

Cervical cancer, the second leading cause of cancer deaths in women, is the consequence of high-risk human papillomavirus (HPV) infections. Toward the development of therapeutic vaccines that can induce both innate and adaptive mucosal immune responses, we analyzed intravaginal (ivag) vaccine delivery of live attenuated
Salmonella enterica
serovar Typhimurium expressing HPV16L1 as a model antigen. Innate immune responses were examined in cervicovaginal tissues by determining gene expression patterns by microarray analysis using nylon membranes imprinted with cDNA fragments coding for inflammation-associated genes. At 24 h, a wide range of genes, including those for chemokines and Th1- and Th2-type cytokine and chemokine receptors were up-regulated in mice ivag immunized with
Salmonella
compared to control mice. However, the majority of transcripts returned to their steady-state levels 1 week after immunization, suggesting a transient inflammatory response. Indeed, cervicovaginal histology of immunized mice showed a massive, but transient, infiltration of macrophages and neutrophils, while T cells were still increased after 7 days. Ivag immunization also induced humoral and antitumor immune responses, i.e., serum and vaginal anti-HPV16VLP antibody titers similar to those induced by oral immunization, and significant protection in tumor protection experiments using HPV16-expressing C3 tumor cells. These results show that ivag immunization with live attenuated
Salmonella
expressing HPV16 antigens modulates the local mucosal gene expression pattern into a transient proinflammatory profile, elicits strong systemic and mucosal immunity against HPV16, and confers protection against HPV16 tumor cells subcutaneously implanted in mice. Examination of the efficacy with which ivag HPV16E7E6
Salmonella
induces regression of tumors located in cervicovaginal tissue is warranted.
The identity of Struthanthus haenkei (Spirostylis haenkei) (Loranthaceae)
Authors: Kuijt Job
Published: March 2008

The name Struthanthus haenkei (Presl) Engler has been variously applied in the past. Study of the type shows it to be synonymous with Struthanthus venetus (H.B.K.) Blume, an amplified description of which is given. The variety angustus Johnston is based on a misinterpretation and is here given separate status as Struthanthus palmeri n. sp.
Scanning electron microscopy of perithecial development in a species of Microsphaera on oak
Authors: Harris James L. , Roth Ivan L.
Published: March 2008

A species of Microsphaera on oak leaf has been examined by scanning electron microscopy. The developing stages of the perithecium and perithecial appendages have been described. The perithecial surface at maturity is marked by ridges of two sizes. Appendages do not appear to be very rigid and are collapsed near the distal end. Multiple dichotomous branching produces an antler-like ornamentation at the appendage end.
Organogénie de la feuille du Begonia radicans Vellozo et du Begonia scabrida (Begoniaceae)
Authors: Barabé Denis , Brouillet Luc , Bertrand Charles
Published: March 2008

The asymmetrical leaf of Begonia raises both biological and mathematical questions. The leaf organogenesis of two species of Begonia is analyzed in this study, one with asymmetrical, palmately nerved leaves, Begonia scabrida A.DC, the other with quasi-symmetrical, pinnately nerved leaves, Begonia radicans Vellozo. Additional observations on Begonia fagifolia Fischer, a species of the second type, are included for comparison. In the three species studied, the leaf primordia are asymmetrical at initiation, notwithstanding mature leaf symmetry or nervation. In B. radicans, the leaf is asymmetrical at initiation and becomes quasi-symmetrical, while in B. scabrida, it remains asymmetrical throughout. The Begonia leaf thus represents a true case of asymmetry, related to the morphogenetic properties of the vegetative apex. None of the present theories of leaf organogenesis are able to fully account for this phenomenon. Leaf asymmetry represents an ontogenetic constraint in the evolutionary history of Begoniaceae. The hypothesis is presented that the palmately nerved leaf is a plesiomorphic state and the pinnately nerved leaf an apomorphic one that appeared repeatedly within the family. Key words: Begoniaceae, leaf, morphogenesis, angiosperm, phylogeny, apex.
Culture, cytology, and reproductive biology of Callithamnion corymbosum (Rhodophyceae, Ceramiaceae) from a western Newfoundland fjord
Authors: Whittick Alan
Published: March 2008

Bonne Bay, Newfoundland, is the northernmost known location for Callithamnion corymbosum in the western Atlantic Ocean. Growth begins in the late summer and plants may overwinter until the following spring; tetrasporangia are produced in November. In culture the species reproduces by tetraspores that regenerate tetrasporangial plants. Tetrasporogenesis occurs under short daylength and is not inhibited by a light break in the middle of the dark cycle; no spore formation occurs under long days. Cytological examination shows ca. 55–60 chromosomes in parent and offspring plants. Microspectrophotofluorometric measurement of nuclear DNA shows no differences in levels between parent and offspring plants. Key words: Rhodophyceae, Callithamnion, asexual, life history, cytology.
Furculomyces, a new homothallic genus of Harpellales (Trichomycetes) from Australian midge larvae
Authors: Lichtwardt Robert W. , Williams Marvin C.
Published: March 2008

A new genus, Furculomyces, is established for two Australian species of trichomycete gut fungi that live in the hindguts of aquatic Chironomidae (Diptera) larvae. The new genus is based primarily on the sexual apparatus consisting of a swollen pair of homothallic conjugants that resemble a wishbone, from which develops a slightly bent biconical zygospore. The type species, Furculomyces boomerangus comb, no v. (basionym: Smittium boomerangum) has been found in Victorian and Tasmanian midges, whereas the new species, Furculomyces westraliensis, is from a midge species in southern Western Australia. These species support other evidence that native Australian gut fungi have a provincial distribution. Key words: Australian, Chironomidae, fungi, Furculomyces, Harpellales, Trichomycetes.
Effects of physical preservation methods on sclerotial germination in Aspergillus flavus and Aspergillus ochraceus in stored grain
Authors: Menasherov M. , Paster N. , Nitzan R.
Published: March 2008

Germination of sclerotia of Aspergillus flavus and Aspergillus ochraceus was assessed following gamma irradiation during exposure to different levels of relative humidities or to various modified atmospheres. The effect of combined treatments on germination was also studied. No sclerotia of either fungi germinated following irradiation with 2.5 kGy. At 80% relative humidity, germination was almost completely inhibited during 50 days of exposure. Sclerotia of A. flavus were found to tolerate higher levels of CO2 than those of A. ochraceus, and 100% germination of the former, but not the latter, occurred at 80% CO2 (given with either 20 or 5% O2). Germination of A. flavus sclerotia was markedly reduced only at modified atmospheres of 40% CO2 and 1% O2. Working with two sublethal dosages of gamma irradiation, 1.0 and 1.5 kGy, it was demonstrated that less CO2 was needed in the atmosphere (with 20% O2) to reduce germination as the irradiation dosage increased. The advantages of the combined treatment compared with each treatment applied alone are discussed. Key words: sclerotia, germination, Aspergillus, inhibition, physical methods.
Early symptoms and resistance of lodgepole pine seedlings inoculated with western gall rust
Authors: Kojwang H. O. , Kamp B. J. van der
Published: March 2008

One-year-old seedlings in 10 open-pollinated Pinus contorta families were inoculated with spores of the rust fungus Endocronartium harknessii at two stages of seedling maturity and two levels of inoculum concentration. The early symptoms (general red stain, red flecks, red streaks) that appeared on the seedlings were recorded 2, 4, and 8 weeks after inoculation, while the number of galls was recorded 1 year after inoculation. The frequency of general red stain and red flecks varied significantly among families. Resistance of families as percent of seedlings producing galls also varied significantly. The frequency of early symptoms was only poorly correlated with family resistance. Also, the occurrence of early symptoms on individual seedlings did not give a good prediction of gall formation on them. These results suggest that early symptoms cannot accurately identify resistant families or individuals. Key words: Endocronartium harknessii, Pinus contorta, symptoms, resistance.
Morphogeographic variation in the Medicago monantha complex
Authors: Small Ernest , Fawzy Manal
Published: March 2008

Morphogeographic variation in the Asian annual Medicago monantha has required clarification. The present numerical taxonomic study in relation to geographical distribution revealed an east–west gradient of the principal correlated characters. Although previous taxonomists had not perceived this gradient as such, in fact it is reflected in traditional taxonomic treatments, i.e., the four commonly recognized subspecies (which are often considered separate species) replace each other in an east–west direction in stepwise overlapping fashion with respect to morphology and geography. The most evident difference observed was with respect to the areas delimited on the surface of the fruit by the intersecting veins; the fruit areoles are more elongated in the western phase than in the east. Given the absence of evident discontinuity or even relative discontinuity in M. monantha, formal delimitation of the traditionally recognized infraspecific taxa seems unjustified. Key words: Medicago monantha, Trigonella, cline, taxonomy, classification, systematics.
Induction photopériodique de l'organogenèse et de la floraison in vitro chez le Cichorium intybus: aspects histologiques
Authors: Mikou Karima , Badila Philippe
Published: March 2008

In root explants of a long-day plant, Cichorium intybus L., grown in vitro, inflorescences were produced under short-day conditions (9 h) if long days were applied on days 10 to 18 of culture. Long days consisted of either 16 h fluorescent light (5.6 W∙m−2) or daily cycles of 9 h white fluorescent plus 15 h red (660 nm, 0.3 W∙m−2) or blue (440 nm, 0.5 W∙m−2) light. The structural changes in the meristems of buds regenerated under these conditions were studied. The influence of photoperiod appeared to be critical between the 10th and 16th days, during the progressive transition from vegetative to prefloral stage, which occurred more rapidly under photoperiodic conditions with red or blue light. In noninductive short days, intermediate meristems could be observed tardily on day 24, but no flower formation took place after transfer to long days. Increasing the quantity of light under short-day conditions up to a level comparable to long-day conditions resulted in a rise in mitotic activity, mainly in the peripheral zone of the meristem, but the vegetative zonation was retained. These data therefore indicate that the duration of light really commits the meristem to the subsequent formation of flower primordia; in contrast, the quantity of light controls the bud formation during the first part of development. Key words: Cichorium, tissue cultures, flowering, meristems, organogenesis, photoperiodism.
Effects of DiPel® 176, a Bacillusthuringiensis subsp. kurstaki (B.t.k.) formulation, on the soil microflora and the fate of B.t.k. in an acid forest soil: a laboratory study
Authors: Visser S. , Addison J.A. , Holmes S.B.
Published: March 2008

The effects of DiPel® 176, a commercially available Bacillusthuringiensis Berliner subsp. kurstaki (B.t.k.) formulation, on microbially mediated carbon and nitrogen mineralization processes, and the persistence of B.t.k. following application of DiPel® 176 to an acidic, coniferous forest soil were evaluated in the laboratory using simple microcosms. Litter (L) and fermentation–humus (FH) material were exposed to DiPel® at the recommended field application rate (FA), DiPel® at 1000× the field application rate (1000× FA), or left untreated. Respiration, substrate induced respiration (SIR), microbial biomass C, metabolic quotients (qCO2), NH4-N, NO3-N, cellulose decay, and B.t.k. viability were monitored regularly over 8 weeks. The FA treatment had no significant impact on soil processes in either the L or FH. The 1000× FA treatment increased SIR and biomass C and decreased qCO2 consistently in both the L and FH. No other effects of the 1000× FA treatment were evident in the L, while in the FH this treatment stimulated respiration initially, then reduced it below control levels; it enhanced cellulose decay; and it inhibited ammonification and nitrification after 8 weeks incubation. In both the L and FH there was no significant loss in viability of B.t.k. in either of the DiPel® treatments over 8 weeks. The microcosms used in this study were simple, inexpensive, and effective, with respiration, SIR, biomass C, and qCO2 being the least variable measurements and the most sensitive to perturbation. This approach is recommended for ecotoxicological and fate testing as outlined in the GuidelinesforRegistrationofNaturallyOccurringMicrobialPestControlAgents.
Containment and concentration of infestations of the western balsam bark beetle, Dryocoetes confusus (Coleoptera: Scolytidae), using the aggregation pheromone exo-brevicomin
Authors: Stock Arthur J. , Borden J.H. , Pratt T.L.
Published: March 2008

Containment and concentration of infestations of the western balsam bark beetle, Dryocoetes confusus Swaine, was demonstrated when (±)-exo-brevicomin released at 0.4 mg/24 h was applied to single subalpine firs, Abieslasiocarpa (Hook.) Nutt., on a 50-m grid over 9-ha blocks, or released at 0.8 mg (24 h/tree)−1 applied to two trees at 50-m centres over the central 4 ha of 16-ha blocks. Nearest-neighbour distance between red trees and newly mass-attacked trees was 24 m in the central 4 ha of baited 16-ha blocks, compared with 13.8 m in control blocks, suggesting a movement of beetles away from "normal" attack centres. Treatments with exo-brevicomin at two trees per spot concentrated 89% of newly mass-attacked trees within 10 m of baited trees, clearly indicating the potential for semiochemical-based management of D. confusus. Within-stand distribution of attacked trees was highly aggregated (Clark–Evans test), in both treated and control blocks. The highly aggregated pattern of attack in control blocks could have been a product of stand structure, and it is hypothesized that D. confusus plays a role in the regeneration of its host by initiating small gaps that favour subalpine fir reproduction. If so, there is potential for using semiochemicals to manipulate D. confusus populations within a patch or selection logging system to maintain cover in climax subalpine forests.
Unbalanced nutrient status and epicuticular wax of Scots pine needles
Authors: Ylimartimo Anneli , Pääkkönen Elina , Holopainen Toini , Rita Hannu
Published: March 2008

Different combinations of normal and excessive foliar levels of nitrogen and normal and deficient foliar levels of K, Mg, and Ca were induced in Scots pine (Pinussylvestris L.) seedlings in an experiment with a completely randomized 24 factorial design during the growing season in 1991 and 1992. For scanning electron microscope analysis of epicuticular wax, the needles were sampled from the same part of the shoot on the same seedlings in September 1991 and 1 year later. The quantity and quality of the structural epicuticular wax were estimated by five-class scales based on the wax coverage or morphology. The effects of foliar nutrients on the quantity and quality of the wax were analyzed by logistic models. The deleterious effect of unbalanced nutrition first became visible in the stomatal furrows; the changes in wax coverage and morphology were clear already one growing season after the start of the nutrient treatments. Changes in the epistomatal chambers did not become discernible until 1 year later. The effect of different nutrients on the wax was somewhat different in stomatal and in nonstomatal areas. Deficiencies of Ca and Mg significantly decreased wax coverage in both the stomatal furrows and epistomatal chambers of the needles. Coverage in the epistomatal chambers was also significantly decreased by K deficiency, N excess, and consequently increased N/K ratios. The wax morphology in both the stomatal furrows and epistomatal chambers changed from tubelike to more fused and netlike structures as a result of deficiencies of K, Mg, and Ca and consequently increased N/K, N/Mg, and N/Ca ratios.
Nitrogen use efficiency in relation to forest type, N expenditure, and climatic gradients in North America
Authors: Yin Xiwei
Published: March 2008

Forest nitrogen use efficiency (NUE) values are often compared along N-availability gradients or between forest types, without adjustment for climate. In this study, NUE (leaf-fall mass/leaf-fall N) was examined with concurrent data on forest type, N expenditure (leaf-fall N), foliar life-span, and major climatic gradients. The hypotheses were that (1) NUE is negatively correlated with N expenditure, (2) NUE is positively correlated with climatic factors such as temperature and light availability, and (3) NUE differs between deciduous and evergreen forests. The data set included 76 deciduous broadleaf forests, 52 evergreen coniferous forests, and 6 mixed forests in North America. All three hypotheses are supported by best-fit models. NUE decreases by about 30% for each doubling of N expenditure for both deciduous and evergreen forests. It increases over 50% in deciduous forests and nearly triples in evergreen forests across the climate data range. Evergreen forests tend to have higher NUEs than deciduous forests only in areas with relatively high temperatures and light availability. This climate–forest type interaction is attributed to contrasts between the forest types in terms of growth period, and regional patterns of foliar N concentration and N resorption.
Rest break in Norway spruce seedlings: test of a dynamic temperature response hypothesis
Authors: Hänninen Heikki , Backman Riitta
Published: March 2008

A hypothesis concerning a dynamic temperature response of rate of rest break was tested using a chilling experiment with three northern provenances of 2-year-old seedlings of Norway spruce (Piceaabies (L.) Karst.). According to the hypothesis, (i) within-population variation exists in the higher threshold for the rest-breaking temperature range and (ii) the higher threshold shifts towards lower temperatures as a result of chilling. The hypothesis was supported by experimental results. The results also indicated that at the beginning of the chilling period the higher threshold is a few degrees above 10 °C in the examined seedling populations. Two conventional theories about the rest period of the trees were unable to explain the observed results. The results facilitate further development of simulation models of rest break and bud burst of the trees.
Dendrochemical response to soil liming in scarlet oak
Authors: Kashuba-Hockenberry Laurie A. , DeWalle David R.
Published: March 2008

To test the hypothesis that the chemical element content of tree rings can record historical chemical changes in soil, wood cores were extracted in 1989 from 65-year-old scarlet oak (Quercuscoccinea Muenchh.) trees located in Moshannon State Forest in central Pennsylvania where soil chemistry had been altered by soil liming. Four wood cores were extracted and composited in 5- to 10-year increments from each of five trees on an untreated control plot and on a plot that had received 1120 kg/ha of Ca as hydrated lime in 1963 and a repeated application on one-half of the plot in 1964. Wood cores were chemically analyzed for 15 elements, using inductively coupled plasma emission spectroscopy. Mn concentrations in tree rings on the limed plot were significantly reduced for up to 16 years following liming. Sr concentrations in tree rings on the limed plot were significantly lower for up to 21 years after liming and up to 10 years before liming. Cu, B, and Pb concentrations were significantly lower on the limed plot in nearly all tree-ring segments. Ca/Al ratios in tree rings were significantly increased for up to 11 years after treatment, but Mg/Al ratios were unaffected. Results suggest that changes in Mn, Sr, and Ca/Al ratios in scarlet oak tree rings can be used to trace soil changes due to liming, but sapwood conduction obscures the exact year of treatment effect.
Interpretation of sugar maple (Acersaccharum) ring chronologies from central and southern Ontario using a mixed linear model
Authors: Ryan D.A.J. , Allen O.B. , McLaughlin D.L. , Gordon A.M.
Published: March 2008

This study presents a new method for assessing the impact of environmental factors on the radial growth rate of trees. The natural logarithm of the specific volume increments (SVI) were fitted to a mixed linear model, which included fixed effects for tree age when the increment occurs, year, precipitation, and temperature both in the year of growth and in the preceding year, and the geographical locale. The model also incorporates stand and tree as random effects. By fitting trees of different ages, the model is able to separate year effects from age effects. Age and year were treated as categorical variables and hence no specific form of growth curve is assumed. The model was fitted to log SVI from 84 mature sugar maple (Acersaccharum Marsh.) trees from 42 uneven-aged stands in six regions of southern and central Ontario representing a known gradient of air pollution. After adjusting for age, precipitation, and temperature effects, the log SVI increased during the first half and declined during the second half of the 20th century in five of the six regions. This suggests that factors other than those included in the model have affected growth. Air pollution remains a likely causal agent in this observed decline.
Effects of mycorrhizal inoculation and fertilizer regime on emergence of Sitka spruce seedlings in bare-root nursery seedbeds
Authors: Ingleby K. , Wilson J. , Mason P.A. , Munro R.C. , Walker C. , Mason W.L.
Published: March 2008

Seedbeds at two Scottish nurseries (Forfar and Newton) were inoculated with the ectomycorrhizal fungus Laccariaproximo (Boud.) Pat. and sown with Sitka spruce (Piceasitchensis (Bong.) Carr.) seed. Numbers of emergent seedlings were affected by both inoculum and fertilizer treatments. Up to 114% more seedlings were found in plots inoculated with live fungus in a vermiculite–peat carrier than in control plots with or without the same carrier. A similar, although reduced, effect was found when the live fungus was encapsulated in alginate beads. Application of fertilizer (to the seedbed before sowing and subsequently as a top dressing) reduced numbers of emergent seedlings at both nurseries; at Forfar, numbers in the treatments that had received fertilizer were 40–50% of the numbers in the analogous unfertilized treatments, while at Newton, the plots that had received live inoculum and fertilizer contained seedling numbers that were 66–72% of those in the comparable unfertilized treatment. The effect of inoculant on seedling numbers occurred within the first few weeks after inoculation and was independent of mycorrhizal formation.
Conversion of dense lodgepole pine stands in west-central British Columbia into young lodgepole pine plantations using prescribed fire. 2. Effects of burning treatments on tree seedling establishment
Authors: Blackwell B. , Feller M.C. , Trowbridge R.
Published: March 2008

The ecological effects of different treatments used to convert dense logdepole pine (Pinusconforta Dougl.) stands into young lodgepole pine plantations are being determined. The treatments used were bulldozing the trees and either broadcast burning the slash or bulldozing the slash into windrows, which were then burned. Burns were conducted under different fuel moisture conditions and state of fuel curing to achieve four classes of fire severity. Lodgepole pine seedling survival was affected by both site preparation and fire severity. Five years after outplanting, survival was significantly (p < 0.05) greater for areas between windrows (81%) than for areas beneath windrows (65%) or for broadcast-burned areas (67%). Survival was greatest after 5 years for low-severity burns in fresh slash (80%) compared with low-severity burns in cured slash and higher severity burns (67–69%). Seedling total height and height increment 5 years after outplanting were significantly greater (p < 0.05) in areas beneath windrows than in areas between windrows or in broadcast-burned areas. However, stem diameter was similar among all site preparation treatments. Fire severity had no effect on lodgepole pine total height, height increment, and basal diameter growth in any year after outplanting. Lodgepole pine seedling foliar nutrient levels were generally consistent with trends in seedling growth in that foliar concentrations generally tended to be higher when growth was higher (in the case of site preparation); however, no significant differences in growth were found (in the case of fire severity). This suggested that foliar nutrient levels could at least partly explain seedling growth results. Surface mineral soil (0–15 cm) chemistry exhibited similar trends to seedling foliar chemistry when site preparation treatments were compared, but not when fire severity classes were compared. This was attributed to foliar chemistry being controlled by factors other than soil chemistry alone.
Localization of tree water uptake in Scots pine and Norway spruce with hydroiogical tracers
Authors: Bishop Kevin , Dambrine Etienne
Published: March 2008

This study explores the potential of hydroiogical tracers for determining the proportion of water uptake by Scots pine (Pinussylvestris L.) and Norway spruce (Piceaabies (L.) Karst.) from different layers in the upper 3 dm of podzolized forest soil. To improve the resolution of the tracer technique, a pair of tracers was employed. One tracer was the naturally occurring vertical gradient in the oxygen isotope ratio,δ18O, of soil solution. The second tracer was a 3H solution placed in the mor layer. A three-component mixing model of water uptake was used to simulate the content of these two tracers in the xylem sap. Each component in the mixing model represented a horizontal layer of soil with a characteristic composition of δ18O and 3H. Two stands were investigated. In both stands, the volume-weighted water uptake by Scots pine occurred at a depth of 8–17 cm in the upper B horizon. This was below the concentration of fine roots in the mor layer and the upper few centimeters of mineral soil. In one of the two study stands, Norway spruce was present. It had mean uptake depths ranging from within the mor layer to 5 cm below the mor–mineral soil contact. An uncertainty in the water uptake depth for each tree of ± 1–2 cm was estimated from a Monte Carlo analysis of uncertainties in the model inputs. In addition to these specific results, the study demonstrated that isotopic tracers provide a simple and effective method for determining the vertical distribution of water uptake.
The economic value of moose hunting in Newfoundland
Authors: Condon Barbara , Adamowicz Wiktor
Published: March 2008

The dichotomous choice contingent valuation method was used to determine the net economic value of moose hunting in Newfoundland. Specific questions addressed the value of changes in moose hunting that could result from forest management. Three statistical models were used to determine mean and median welfare measures for four different contingent valuation models. The values obtained are similar to other studies that have obtained economic values for big-game hunting. The results show that although differences in welfare measures exist between statistical models, the mean and median values within a specification appear to be relatively robust. The results also suggest that factors affected by forest management (e.g., moose populations) provide more substantial benefits than factors under the control of the administrative agency (e.g., season length).
INFINITE DIMENSIONAL KRAWCZYK OPERATOR FOR FINDING PERIODIC ORBITS OF DISCRETE DYNAMICAL SYSTEMS
Authors: GALIAS ZBIGNIEW , ZGLICZYŃSKI PIOTR
Published: March 2008

In this work, we introduce the Krawczyk operator for infinite dimensional maps. We prove two properties of this operator related to the existence of zeros of the map. We also show how the Krawczyk operator can be used to prove the existence of periodic orbits of infinite dimensional discrete dynamical systems and for finding all periodic orbits with a given period enclosed in a specified region. As an example, we consider the Kot–Schaffer growth-dispersal model, for which we find all fixed points and period-2 orbits enclosed in the region containing the attractor observed numerically.
BIFURCATION ANALYSIS AND CHAOS CONTROL FOR LÜ SYSTEM WITH DELAYED FEEDBACK
Authors: XIAO MIN , CAO JINDE
Published: March 2008

Time-delayed feedback has been introduced as a powerful tool to control unstable periodic orbits or control unstable steady states. In the present paper, regarding the delay as a parameter, we investigate the effect of delay on the dynamics of Lü system with delayed feedback. After the effect of delay on the steady states is analyzed, Hopf bifurcation is studied, where the direction, stability and other properties of the bifurcating periodic solutions are determined by using the normal form theory and the center manifold theorem. Finally, we provide several numerical simulations, which indicate that when the delay passes through certain critical values, chaotic oscillation is converted into a stable steady state or a stable periodic orbit.
ANTI-PHASE SYNCHRONIZATION OF INHIBITORILY COUPLED NEURONS
Authors: SHI XIA , LU QISHAO , CHEN GUANRONG
Published: March 2008

Some new insights into the anti-phase synchronization of a network of inhibitorily coupled neurons are presented by means of qualitative analysis and numerical simulation. The network, which satisfies three significant conditions, gives rise to typical anti-phase synchronous solutions. By using the geometric method of dynamical systems, each corresponding reduced network model is analyzed, and a special and important parameter region, called P*-jumping up region, is identified. In terms of some basic properties of the P*-jumping up region, two conditions for the neuron states to enter this region are given. These conditions can be satisfied by adjusting a parameter K that controls the decay speed of the inhibitory coupling. Furthermore, it is concluded that if the parameter K is chosen so as to satisfy the two conditions, then two neurons will achieve anti-phase synchronous oscillation, independent of the initial conditions.
CHAOS FOR DISCRETE-TIME RTD-BASED CELLULAR NEURAL NETWORKS
Authors: CHEN FENG-JUAN , LI JI-BIN , CHEN FANG-YUE
Published: March 2008

In this letter, a model of discrete-time RTD-based cellular neural networks is considered. The chaotic behavior related to the existence of snap-back repellers given by Marotto's theorem is rigorously proved. The parameter regions exhibiting chaotic dynamics are determined.
GLOBAL EXPONENTIAL STABILITY CONDITIONS FOR DELAYED PARABOLIC NEURAL NETWORKS WITH VARIABLE COEFFICIENTS
Authors: LOU XUYANG , CUI BAOTONG
Published: March 2008

In this paper, we present a class of delayed parabolic neural networks (DPNN) with variable coefficients. Some sufficient conditions for the global exponential stability of the DPNN with variable coefficients are derived by a method based on delay differential inequality. The method, which does not make use of Lyapunov functionals, is simple and effective for the stability analysis of DPNN with variable coefficients.
A THEORETICAL APPROACH OF THE PROPAGATION THROUGH GEOMETRICAL CONSTRAINTS IN CARDIAC TISSUE
Authors: JACQUIR S. , BINCZAK S. , BILBAULT J. M. , ATHIAS P.
Published: March 2008

The behavior of impulse propagation in the presence of nonexcitable scars and boundaries is a complex phenomenon and induces pathological consequences in cardiac tissue. In this article, a geometrical configuration is considered so that cardiac waves propagate through a thin strand, which is connected to a large mass of cells. At this interface, waves can slow down or even be blocked depending on the width of the strand. We present an analytical approach leading to determine the blockade condition, by introducing planar traveling wavefront and circular stationary wave. Eventually, the influence of the tissue geometry is examined on the impulse propagation velocity.
RELIC RADIATION FROM AN EVAPORATING BLACK HOLE
Authors: FARLEY A. N. ST. J. , D'EATH P. D.
Published: March 2008

This paper presents a non-string-theoretic calculation of the microcanonical entropy of relic integer-spin Hawking radiation, at fixed total energy E, from an evanescent, neutral, non-rotating four-dimensional black hole. The only conserved macroscopic quantity is the total energy E which, for a black hole that evaporates completely, is the total energy of the relic radiation. Through a boundary-value approach, in which data for massless, integer-spin perturbations are set on initial and final space-like hypersurfaces, the statistical-mechanics problem becomes, in effect, a one-dimensional problem, with the "volume" of the system determined by the real part of the time separation at spatial infinity — the variable conjugate to the total energy. We count the number of field configurations on the final space-like hypersurface that have total energy E, assuming that initial perturbations are weak. We find that the density of states resembles the well-known Cardy formula. The Bekenstein–Hawking entropy is recovered if the real part of the asymptotic time separation is of the order of the semi-classical black-hole lifetime. We thereby obtain a statistical interpretation of black-hole entropy. Corrections to the microcanonical entropy are computed, and we find agreement with other approaches in terms of a logarithmic correction to the black-hole area law, which is universal (independent of black-hole parameters). This result depends crucially upon the discreteness of the energy levels. We discuss the similarities of our approach with the transition from the black-hole to the fundamental-string regime in the final stages of black-hole evaporation. In addition, we find that the squared coupling, g2, which regulates the transition from a black hole to a highly-excited string state, and vice versa, can be related to the angle, δ, in the complex-time plane, through which we continue analytically the time separation at spatial infinity. Thus, in this scenario, the strong-coupling regime corresponds to a Euclidean black hole, while the physical limit of a Lorentzian space–time (the limit as δ → 0+) corresponds to the weak-coupling regime. This resembles the transition of a black hole to a highly-excited string-like state, which subsequently decays into massless particles, thereby avoiding the naked singularity.
UV/IR MIXING AND BLACK HOLE THERMODYNAMICS
Authors: NOZARI KOUROSH , FAZLPOUR BEHNAZ
Published: March 2008

The goal of this paper is to investigate the final stage of the black-hole-evaporation process in the framework of Lorentz-violating modified dispersion relations (MDRs). As a consequence of MDRs, the high energy sector of the underlying field theory does not decouple from the low energy sector — a phenomenon known as UV/IR mixing. In the absence of exact supersymmetry, we derive an MDR which shows UV/IR mixing by a novel energy dependence. Then we investigate the effects of this type of MDRs on the thermodynamics of a radiating noncommutative Schwarzschild black hole. The final stage of black hole evaporation obtained in this framework is compared with existing pictures.