bluuebunny/crossref_metadata_2025 huggingface dataset:
Forward-masked spatial tuning curves in cochlear implant users
Authors: Nelson David A. , Donaldson Gail S. , Kreft Heather
Published: March 2008

Forward-masked psychophysical spatial tuning curves (fmSTCs) were measured in twelve cochlear-implant subjects, six using bipolar stimulation (Nucleus devices) and six using monopolar stimulation (Clarion devices). fmSTCs were measured at several probe levels on a middle electrode using a fixed-level probe stimulus and variable-level maskers. The average fmSTC slopes obtained in subjects using bipolar stimulation (3.7dB∕mm) were approximately three times steeper than average slopes obtained in subjects using monopolar stimulation (1.2dB∕mm). Average spatial bandwidths were about half as wide for subjects with bipolar stimulation (2.6mm) than for subjects with monopolar stimulation (4.6mm). None of the tuning curve characteristics changed significantly with probe level. fmSTCs replotted in terms of acoustic frequency, using Greenwood’s [J. Acoust. Soc. Am. 33, 1344–1356 (1961)] frequency-to-place equation, were compared with forward-masked psychophysical tuning curves obtained previously from normal-hearing and hearing-impaired acoustic listeners. The average tuning characteristics of fmSTCs in electric hearing were similar to the broad tuning observed in normal-hearing and hearing-impaired acoustic listeners at high stimulus levels. This suggests that spatial tuning is not the primary factor limiting speech perception in many cochlear implant users.
Improved prewhitening method for linear frequency modulation reverberation using dechirping transformation
Authors: Choi Byung Woong , Bae Eun Hyon , Kim Jeong Soo , Lee Kyun Kyung
Published: March 2008

This letter presents an autoregressive (AR) prewhitener for linear frequency modulation (LFM) reverberation to enhance the target signal. The proposed method uses a dechirping transformation to inversely compensate the frequency chirp rate of the LFM and give the LFM reverberation a stationary frequency property in each data block. The left or right beam signal adjacent to the current beam is then used as the reference signal, and the frequency response of each data block modeled using the AR coefficients. Finally, these coefficients are used to implement the inverse filter and efficiently prewhiten the LFM reverberation of the current beam.
Pharmacodynamic Analysis and Clinical Trial of Amoxicillin Sprinkle Administered Once Daily for 7 Days Compared to Penicillin V Potassium Administered Four Times Daily for 10 Days in the Treatment of Tonsillopharyngitis Due to
Streptococcus pyogenes
in Children
Authors: Pichichero M. E. , Casey J. R. , Block S. L. , Guttendorf R. , Flanner H. , Markowitz D. , Clausen S.
Published: March 2008

An a priori pharmacokinetic/pharmacodynamic (PK/PD) target of 40% daily time above the MIC (
T
>MIC; based on the MIC
90
of 0.06 μg/ml for
Streptococcus pyogenes
reported in the literature) was shown to be achievable in a phase 1 study of 23 children with a once-daily (QD) modified-release, multiparticulate formulation of amoxicillin (amoxicillin sprinkle). The daily
T
>MIC achieved with the QD amoxicillin sprinkle formulation was comparable to that achieved with a four-times-daily (QID) penicillin VK suspension. An investigator-blinded, randomized, parallel-group, multicenter study involving 579 children 6 months to 12 years old with acute streptococcal tonsillopharyngitis was then undertaken. Children were randomly assigned 1:1 to receive either the amoxicillin sprinkle (475 mg for ages 6 months to 4 years, 775 mg for ages 5 to 12 years) QD for 7 days or 10 mg/kg of body weight of penicillin VK QID for 10 days (up to the maximum dose of 250 mg QID). Unexpectedly, the rates of bacteriological eradication at the test of cure were 65.3% (132/202) for the amoxicillin sprinkle and 68.0% (132/194) for penicillin VK (95% confidence interval, −12.0% to 6.6%). Thus, neither antibiotic regimen met the minimum criterion of ≥85% eradication ordinarily required by the U.S. FDA for first-line treatment of tonsillopharyngitis due to
S. pyogenes
. The results of subgroup analyses across demographic characteristics and current infection characteristics and by age/weight categories were consistent with the primary-efficacy result. The clinical cure rates for amoxicillin sprinkle and penicillin VK were 86.1% (216/251) and 91.9% (204/222), respectively (95% confidence interval, −11.6% to −0.4%). The results of a post hoc PD analysis suggested that a requirement for 60% daily
T
>MIC
90
more accurately predicted the observed high failure rates for bacteriologic eradication with the amoxicillin sprinkle and penicillin VK suspension studied. Based on the association between longer treatment courses and maximal bacterial eradication rates reported in the literature, an alternative composite PK/PD target taking into consideration the duration of therapy, or total
T
>MIC, was considered and provides an alternative explanation for the observed failure rate of amoxicillin sprinkle.
Buthionine Sulfoximine Has Anti-
Trypanosoma cruzi
Activity in a Murine Model of Acute Chagas' Disease and Enhances the Efficacy of Nifurtimox
Authors: Faúndez Mario , López-Muñoz Rodrigo , Torres Gloria , Morello Antonio , Ferreira Jorge , Kemmerling Ulrike , Orellana Myriam , Maya Juan D.
Published: March 2008

l
-Buthionine (
S
,
R
)-sulfoximine (BSO) at a dose of 220 mg/kg of body weight/day showed an anti-
Trypanosoma cruzi
effect in infected mice, increasing their survival rate and decreasing the parasitemias and parasite burden in the hearts. Treatment with BSO plus nifurtimox caused an increase in the survival rate in comparison to the rates with treatment with each drug alone.
Toll-Like Receptor 9-Dependent Immune Activation by Unmethylated CpG Motifs in
Aspergillus fumigatus
DNA
Authors: Ramirez-Ortiz Zaida G. , Specht Charles A. , Wang Jennifer P. , Lee Chrono K. , Bartholomeu Daniella C. , Gazzinelli Ricardo T. , Levitz Stuart M.
Published: March 2008

Phagocytic defenses are critical for effective host defenses against the opportunistic fungal pathogen
Aspergillus fumigatus
. Previous studies found that following challenge with
A. fumigatus
, Toll-like receptor 9 (TLR9) knockout mice survived longer than wild-type mice. However, the mechanism responsible was not defined. Here we demonstrate that
A. fumigatus
contains unmethylated CpG sequences, the natural ligands for TLR9.
A. fumigatus
DNA and synthetic CpG-rich oligodeoxynucleotides (ODNs) containing sequences found in the
A. fumigatus
genome potently stimulated the production of proinflammatory cytokines in mouse bone marrow-derived dendritic cells (BMDCs) and human plasmacytoid dendritic cells. The response was decreased when the fungal DNA was treated with a CpG methylase or with CpG-specific endonucleases. A role for TLR9 was demonstrated as cytokine production was abolished in BMDCs from TLR9-deficient mice. Moreover, transfection of HEK293 cells with human TLR9 conferred responsiveness to synthetic CpG-rich ODNs containing sequences found in
A. fumigatus
DNA. Taken together, these data demonstrate that TLR9 detects
A. fumigatus
DNA, resulting in the secretion of proinflammatory cytokines, which may contribute to the immune response to the pathogen.
Single Nucleotide Polymorphisms That Cause Structural Changes in the Cyclic AMP Receptor Protein Transcriptional Regulator of the Tuberculosis Vaccine Strain
Mycobacterium bovis
BCG Alter Global Gene Expression without Attenuating Growth
Authors: Hunt Debbie M. , Saldanha José W. , Brennan John F. , Benjamin Pearline , Strom Molly , Cole Jeffrey A. , Spreadbury Claire L. , Buxton Roger S.
Published: March 2008

Single nucleotide polymorphisms (SNPs) are present in the global transcriptional regulator cyclic AMP (cAMP) receptor protein (CRP) of the attenuated vaccine strain
Mycobacterium bovis
, bacillus Calmette-Guérin (BCG). We have found that these SNPs resulted in small but significant changes in the expression of a number of genes in
M. tuberculosis
when a deletion of the Rv3676 CRP was complemented by the BCG allele, compared to complementation by the
M. tuberculosis
allele. We can explain these changes in gene expression by modeling the structure of the mycobacterial protein on the known structure of CRP from
Escherichia coli
. Thus, the SNP change in the DNA-binding domain, Lys178, is predicted to form a hydrogen bond with the phosphate backbone of the DNA, as does the equivalent residue in
E. coli
, whereas Glu178 in
M. tuberculosis
/
M. bovis
does not, thus explaining the stronger binding reported for CRP of BCG to CRP-binding sites in mycobacterial DNA. In contrast, the SNP change in the nucleotide binding domain (Leu47Pro) is predicted to result in the loss of one hydrogen bond, which is accommodated by the structure, and would not therefore be expected to cause any change in function relating to cAMP binding. The BCG allele fully complemented the growth defect caused by the deletion of the Rv3676 protein in
M. tuberculosis
, both in vitro and in macrophage and mouse infections, suggesting that these SNPs do not play any role in the attenuation of BCG. However, they may have allowed BCG to grow better under the in vitro-selective conditions used in its derivation from the
M. bovis
wild type.
The Intrinsic Immunoglobulin G Endopeptidase Activity of Streptococcal Mac-2 Proteins Implies a Unique Role for the Enzymatically Impaired Mac-2 Protein of M28 Serotype Strains
Authors: Söderberg Jenny Johansson , Engström Patrik , von Pawel-Rammingen Ulrich
Published: March 2008

IdeS, a secreted cysteine protease of the important human pathogen
Streptococcus pyogenes
, interferes with phagocytic killing by specifically cleaving the heavy chain of immunoglobulin G (IgG). Two allelic variants of the enzyme have been described, the IgG-specific endopeptidase, IdeS (or Mac-1) and Mac-2, a protein with only weak IgG endopeptidase activity, which has been suggested to interfere with opsonophagocytosis by blocking Fcγ receptors of phagocytic cells. However, despite the fact that Mac-2 proteins interact with Fcγ receptors, no inhibition of reactive oxygen species (ROS) production, opsonophagocytosis, or streptococcal killing by Mac-2 has been reported. In the present study, Mac-2 proteins are shown to contain IgG endopeptidase activity indistinguishable from the enzymatic activity exhibited by IdeS/Mac-1 proteins. The earlier reported weak IgG endopeptidase activity appears to be unique to Mac-2 of M28 serotype strains (Mac-2
M28
) and is most likely due to the formation of a disulfide bond between the catalytic site cysteine and a cysteine residue in position 257 of Mac-2
M28
. Furthermore, Mac-2 proteins are shown to inhibit ROS production ex vivo, independently of the IgG endopeptidase activity of the proteins. Inhibition of ROS generation per se, however, was not sufficient to mediate streptococcal survival in bactericidal assays. Thus, in contrast to earlier studies, implicating separate functions for IdeS and Mac-2 protein variants, the current study suggests that Mac-2 and IdeS are bifunctional proteins, combining Fcγ receptor binding and IgG endopeptidase activity. This finding implies a unique role for Mac-2 proteins of the M28 serotype, since this serotype has evolved and retained a Mac-2 protein lacking IgG endopeptidase activity.
Lateral bud growth on excised stem segments: effect of the stem
Authors: Peterson Carol A. , Fletcher R. A.
Published: March 2008

Lateral buds at the cotyledonary nodes of soybean plants grown under the conditions used in this study usually remain inhibited. These buds grow when the apical part of the plant is removed. They will grow, but less strongly, when the roots as well as the apex of the plant are removed and the basal end of the cut stem is placed in a mineral salt solution. Bud growth is further diminished by decreasing the length of stem left attached to the bud. The cotyledon is essential for bud growth on plant segments maintained in nutrient solution, but it can be replaced by a 1% sucrose solution during the early days of bud growth. Buds which are completely detached from the stem and placed in 1% sucrose do not elongate, but a small number of cell divisions are detectable, indicating that the early events of the release from inhibition have occurred. Buds elongate when they are apically or centrally located on stem segments. Increasing the length of the attached stem segments increases the growth of the buds. Additions of the cytokinin benzyladenine to plants causes a dramatic increase in bud growth when buds are attached to stem segments but does not stimulate growth of buds without stem segments. It is concluded that benzyladenine alone will not substitute for a factor(s) present in the stem which is necessary for bud growth. Increasing stem lengths above buds located at the basal ends of segments inhibits bud growth. It is suggested that this may be due to an accumulation of endogenous auxin at the site of the buds.
Demography of a jack pine stand
Authors: Yarranton M. , Yarranton G. A.
Published: March 2008

The demography of a jack pine, Pinus banksiana, stand established after a fire in 1915 was reconstructed by estimating the ages of dead trees. The survivorship curve is nonlinear and mortality rates rise linearly from 18 to 47 years after the fire and then decline. A balance between intensification of competition and increasing regularity of distribution of surviving trees may account for this. Causes of death appear to be drought stress and physical damage from ice storms.
Life cycle and age structure of ramets in an expanding population of Salix exigua (sandbar willow)
Authors: Ottenbreit Kimberley A. , Staniforth Richard J.
Published: March 2008

The sandbar willow (Salix exigua Nuttall, ssp. interior (Rowlee) Cronquist) is a dominant woody pioneer and stabilizer of riverbanks and sand dunes over much of North America. The growth rates, life-history phases, sex ratio, longevity, and age structure of a large population growing on a point bar in the Assiniboine River, Manitoba were assessed. Average annual height increments were 29.7 cm, and average annual girth increments were 2.6 mm/year. There were no significant differences between sexes. Significant linear correlations existed between basal stem diameter and age and between stem height and age. Flowering occurred in a few 2- and 3-year-old stems, regardless of sex. Flowering frequency increased to 93% at the age of 9 years. Stem mortality was highest in 3-, 4-, and 6-year-old ramets, and senescence was first observed at about 12 years. Though few stems at this site were older than 12 years, the oldest stem encountered was 31 years old and had sprouted soon after the point bar had started to form. The sex ratio of 1.7:1.0 significantly favoured males. Key words: willow, Salix, population dynamics, age structure, life cycle, sex ratio, clonal, ramets.
Recent dynamics of jack pine at its northern distribution limit in northern Quebec
Authors: Desponts Mireille , Payette Serge
Published: March 2008

The northernmost jack pine (Pinus banksiana Lamb.) populations in northern Quebec are located at the boreal forest–forest tundra boundary, along the Grande rivière de la Baleine, where they colonize the sandy terraces affected by recurrent fires. The recent fire history in the study area, as deduced from fire scar and age structure data, spans a 216-year period from 1773 to 1988. Forest fires occurred on the sites at intervals averaging 40 to 80 years. The analysis of 19 coniferous stands (jack pine and black spruce (Picea mariana (Mill.) Bsp)) indicated that forest communities younger than 67 years old were open jack pine – Cladina mitis or jack pine – black spruce – C. mitis woodlands, while the oldest stands, more than 132 years old, were dominated by jack pine, black spruce, and Cladina stellaris. Stands less than 67-years-old had an age structure almost normally distributed and regeneration often occurred within less than 30 years after fire in both species, while most stands older than 132 years had a multiaged structure. In sites with a prolonged fire-free interval, jack pine was overgrown by black spruce. Spruce woodlands have developed on sites where the organic layer was relatively thick and continuous and they are the end result of the postfire successional process. However, at several sites both conifer species showed an ability to regenerate in prolonged absence of fire disturbance, particularly in open sites with exposed mineral substrates. At the regional scale, fire frequency during the last 200 years has been high enough to prevent pine exclusion at its range limit. The key requirement for the long-term maintenance of jack pine populations is that fires return at intervals shorter than the average life-span of individual trees. It is concluded that the northernmost jack pine populations are able to maintain and regenerate under present fire conditions. Key words: fire, subarctic, jack pine, postfire regeneration, boreal forest.
Characterization of universally avirulent strains of Phytophthora sojae
Authors: Bhat Ravindra G. , Olah Arthur F. , Schmitthenner August F.
Published: March 2008

During the process of selfing race 1 of Phytophthora sojae M. J. Kaufmann & J. W. Gerdemann, a pathogen of soybean (Glycine max (L.) Merr.), a 3:1 segregation ratio of race 1 to avirulence was obtained. Avirulent strains were identical in appearance to races 1, 3, and 4 but induced the hypersensitive response when inoculated on the universally susceptible soybean cultivar Williams. A representative avirulent strain did not cause disease on cultivars with known Rps (resistance to P. sojae) genes or gene combinations, or on 33 plant introductions that were susceptible to race 1. The avirulent strain rotted apples in a manner similar to races 1 and 4 and did not rot soybean pods similar to avirulent races. It induced the hypersensitive response in soybean cotyledons, which then rotted after being placed in flooded conditions. Seventy-eight typical avirulent single-oospore strains of P. sojae and Phytophthora and Pythium spp. induced the hypersensitive response and elicited as much glyceollin in 'Williams' and 'Williams 79' as races 1, 3, and 4 elicited in 'Williams'. Four Phytophthora spp., which caused some seedling rot of soybean, elicited levels of glyceollin as high as races 1 and 3 in 'Williams 79'. It is concluded that the avirulent strains obtained from race 1 are either pathogenic and have host-specificity for soybean or universally avirulent strains that have lost all race-specific virulence genes. Key words: Phytophthora sojae, soybean, pathogens, races, hypersensitivity, plant – microbe interactions.
Direct somatic embryogenesis and regeneration of plants from seedling explants of peanut (Arachis hypogaea): promotive role of thidiazuron
Authors: Gill R. , Saxena Praveen K.
Published: March 2008

An efficient procedure has been developed for inducing direct somatic embryogenesis, organogenesis, and regeneration of plants from tissue cultures of peanut (Arachis hypogaea L.). Thin transverse sections of the cotyledons and juvenile leaves were cultured on Murashige and Skoog medium supplemented with N6-benzylaminopurine (BAP) or a substituted phenylurea, thidiazuron (TDZ). Somatic embryos or shoot buds differentiated from cut surfaces of the cotyledons and midrib region of the leaves. The application of BAP induced differentiation of shoot buds whereas the treatment with TDZ resulted in the production of somatic embryos. Somatic embryos developed into plants after subculturing on a basal meduim. Agar-solidified medium was found to be superior to the liquid medium for the development of embryos and shoot buds. The procedure of TDZ-induced somatic embryogenesis and plant regeneration was successfully applied to three genotypes of peanut. A distinct feature of this study is the induction of the morphogenic competence in cultures of seedling expiants of peanut that so far have remained recalcitrant to somatic embryogenesis in vitro. Key words: peanut, Arachis hypogaea, shoot regeneration, somatic embryogenesis, thidiazuron, plant regeneration.
Smittium bullatum from a New Zealand midge larva and new records of other trichomycete gut fungi
Authors: Lichtwardt Robert W. , Williams Marvin C.
Published: March 2008

An apparently uncommon gut fungus, Smittium bullatum (Trichomycetes, Harpellales), is described from Chironomidae (Orthocladiinae) larvae living in South Island, New Zealand, streams. Records of other Harpellales in South Island aquatic insects are reported, including the presence of zygospores of the New Zealand species Pennella asymmetrica from Simuliidae larvae. The richness of some harpellid gut fungi in New Zealand is compared with that in Australia and other parts of the world, and the biogeography of Smittium is discussed. Key words: biogeography, Chironomidae, Diptera, New Zealand, Smittium, Trichomycetes.
Latitudinal trends in acorn size in eastern North American species of Quercus
Authors: Aizen Marcelo A. , Woodcock Hilary
Published: March 2008

Latitudinal variation in acorn size was examined in 32 species of the genus Quercus geographically restricted to eastern North America. Within-species comparisons showed the existence of a prevalent trend: individuals at high latitude produce, on the average, smaller acorns than individuals of the same species at low latitude. This observed trend, clines of decreasing acorn size with increasing latitude, could represent (i) the selected or plastic response to a shorter and (or) cooler growing season constraining the size of acorns that can mature on a tree, (ii) a consequence of past size-selective dispersal that accompanied postglacial range expansion, or (iii) a combination of these effects. The within-species trend contrasted with an observed among-species trend: species with large acorns have ranged that extend into higher latitudes than species with small acorns. Current evidence strongly suggests that small acorn size is maladaptive for successful seedling establishment at higher latitudes. Our results caution against inferring selective forces operating on seed size from among-species comparisons. Key words: acorn size, Quercus L., latitudinal clines, eastern North America.
Ultrastructure of Pyramimonas cyrtoptera sp.nov. (Prasinophyceae), a species with 16 flagella from northern Foxe Basin, Arctic Canada, including observations on growth rates
Authors: Daugbjerg Niels , Moestrup Øjvind
Published: March 2008

A new species of the genus Pyramimonas is reported from the Canadian Arctic, the first record of Pyramimonas from northern Foxe Basin, Northwest Territories. The general structure of the cell and six types of scales are described. Pyramimonas cyrtoptera sp.nov. is remarkable in possessing 16 flagella, two chloroplasts, two pyrenoids, and two pairs of eyespots of unequal size. It is the largest known species of Pyramimonas, measuring 38–42 μm in length. The presence of 16 flagella and two chloroplasts sets it apart from all other species of Pyramimonas. Pyramimonas cyrtoptera belongs to the subgenus Pyramimonas. A new type of hair scale is reported for members of this group. The growth responses of P. cyrtoptera to variations in temperature and salinity indicate that it is as cold stenothermal and euryhaline. Key words: Prasinophyceae, Pyramimonas, flagella, Arctic Canada, temperature, salinity.
Effect of stem bending on hydraulic conductivity and wood strength of loblolly pine
Authors: Fredericksen T.S. , Hedden R.L. , Williams S.A.
Published: March 2008

Stems of 30-year-old loblolly pine (Pinustaeda L.) trees were bent with a winch to determine the effect of bending, which might occur from severe wind stress, on the hydraulic conductivity and wood strength of tree stems. Stems were bent to a point of imminent stem failure and then released. After release, stems leaned an average of 6.25° from their original vertical position. Measurements of sapwood permeability and viable conducting area were made on stem sections cut from bent trees and were compared with sections taken from unstressed (control) trees. Dye was used to determine the percentage of functional conducting elements. An average loss of approximately 30% in conducting sapwood area was attributed to the bending treatment. Loss of functional conducting area was greater along the axis of bending than on the lateral sides of the stem perpendicular to the direction of bending. Damage was greatest on the compression side of the stem. Despite this damage, no difference was observed in sapwood permeability due to treatment. Modulus of elasticity and modulus of rupture were reduced by 19% and 34%, respectively, on the compression side of bent stems compared with control stems. Loblolly pine appears to be capable of sustaining significant damage to its water conducting system without compromising its hydraulic conductivity. However, reduced wood strength due to bending may result in increased susceptibility to wind breakage and (or) decreased commercial value.
Stand and tree characteristics and stockability in Pinustaeda plantations in Hawaii and South Carolina
Authors: Harms William R. , DeBell Dean S. , Whitesell Craig D.
Published: March 2008

Stand structure and crown architecture of loblolly pine (Pinustaeda L.) spacing trials in Hawaii and South Carolina were examined for attributes that would explain markedly different stockabilities (stand density per mean stand DBH), respectively, 1740 and 850 trees/ha at a quadratic mean stand DBH of 25 cm. In plots spaced at 2.4 × 2.4 m, these stockabilities produced 604 m3/ha at age 25 in Hawaii, and 297 m3/ha in South Carolina. Data collected in these stands indicate that stockability differences were associated with differences in tree size-class structure, crown length, and leaf area. Both stands were characterized by a two-tiered height structure, but the crown bases of trees in the subdominant class in Hawaii extended 1–2 m below the bases of the crowns of the dominant height class. In the South Carolina stands the crown bases of both height classes were at the same level. Green crown lengths in Hawaii were 4–7 m longer than in South Carolina, and the associated crown leaf area of 63.9 m2 was five times greater. The differences in stockability was attributed to the Hawaiian site and climate, which provide a long growing season, high solar radiation, high sun angle, favorable temperatures, and a favorable soil moisture regime and foliage nutrient status, and to a lack of significant insect and disease pests. The influence of genotype on stockability was not testable with these data.
Water relations parameters of lowland and upland black spruce: seasonal variations and ecotypic differences
Authors: Abidine A. Zine El , Bernier P.Y. , Plamondon A.P.
Published: March 2008

Weekly values of water relations parameters of four black spruce (Piceamariana (Mill.) B.S.P) populations growing in a common garden north of Québec City were obtained by pressure–volume curve analysis from mid-May to mid-October 1991. Two of the four populations originated from the province of Quebec, and two were from Ontario. Within each geographical location, one population was from a lowland site (peat soil) and the other from an upland site (well-drained sandy soil). Differences between upland and lowland populations were small but statistically significant for the majority of water relations parameters in the Ontario pair. No significant differences could be found between populations in the Quebec pair. In the Ontario pair, trees from the lowland site exhibited some traits that could be associated with water-stress tolerance, such as lower relative water content at turgor loss point, lower maximum modulus of elasticity, lower osmotic potential at turgor loss point, and higher osmotic amplitude for turgor maintenance. The seasonal pattern of water relations parameters was similar among the four populations and also similar to patterns that have been reported for other species. The seasonal variations in water relations parameters followed phenological changes that were driven by seasonal shifts in environmental parameters.
Response of live oak selections to inoculation with Ceratocystisfagacearum
Authors: Greene T.A. , Appel D.N.
Published: March 2008

Progeny from 26 live oak (Quercusvirginiana Mill. and Quercusfusiformis Small) were inoculated with conidia of Ceratocystisfagacearum (T.W. Bretz) J. Hunt. in two trials. The oaks were either superior selections, slow-growing selections rejected from a tree improvement program, postepidemic survivors in an oak wilt center, or preepidemic trees outside the oak wilt center. Symptom development was monitored for 244 and 99 days in the two trials. Seedlings from the postepidemic population survived significantly better than those from the preepidemic trees. Considerable diversity existed among the responses of the superior selections tested. In general, seedlings from the pre- and post-epidemic populations developed symptoms faster than seedlings from the tree improvement program; however, rapidity of symptom development was not a good predictor of final survival. Postepidemic seedlings survived as well as selections in one trial and better than most selections in the other trial.
Fall lifting and long-term freezer storage of ponderosa pine seedlings: effects on starch, root growth, and field performance
Authors: Omi Steven K. , Rose Robin , Sabin Thomas E.
Published: March 2008

To determine the response of seedlings lifted in fall and stored at temperatures below 0 °C until outplanting, ponderosa pine (Pinusponderosa Dougl. ex Laws.) seedlings from two Oregon seed sources were harvested in September, October, and November (stored below 0 °C until late winter–spring planting) and compared with seedlings lifted in March (stored above 0 °C until planting). Growth potential at the time of planting was measured by monitoring changes in root initiation, fresh weight, and root starch concentration and content under greenhouse conditions. Field performance was determined by measuring survival and growth at two field sites. Dry weight and root starch decreased 5–13% and 82–99%, respectively, in storage, and the majority of change occurred during the first 3 months of storage. Less than 15% of the seedlings from the September lifting and storage treatment initiated new roots, and fresh weight decreased more than 30% during the greenhouse test. Seedlings from this treatment had less than 25% field survival during the 1st and 2nd years after outplanting. Greater than 62% of seedlings lifted in late fall and spring had new roots; these seedlings exhibited less than 14% loss in fresh weight, and greater than 75% field survival. In the greenhouse test, initial root starch concentration was not related to subsequent root growth (new root weight or days to root initiation). Similarly, neither initial root starch concentration nor content at the time of planting was strongly associated with field survival or growth in the field after planting.
Photosynthesis, water relations, and leaf morphology of xeric versus mesic Quercusrubra ecotypes in central Pennsylvania in relation to moisture stress: Discussion of sample size, sampling, and statistical analyses in a physiological genetics paper
Authors: Seiler J.R. , Johnsen K.H.
Published: March 2008

not available
Monoterpene composition and fusiform rust resistance in slash and loblolly pines
Authors: Michelozzi M. , White T.L. , Squillace A.E. , Lowe W.J.
Published: March 2008

Monoterpene composition of cortical tissue was analyzed in slash pine (Pinuselliottii Engelm. var. elliottii) and loblolly pine (Pinustaeda L.) clones with known breeding values for fusiform rust resistance. Trees having a relatively high content of β-phellandrene tend to be more resistant than trees with a low β-phellandrene content. Such results confirm previous data and suggest the utilization of β-phellandrene content as an aid in selecting relatively rust resistant slash and loblolly pines.
Preliminary DRIS norms for coastal Douglas-fir soils in Washington and Oregon
Authors: Shumway J.S. , Chappell H.N.
Published: March 2008

The Diagnosis and Recommendation Integrated System (DRIS) has been used successfully in agricultural crops and holds promise for use in forest stands. This study used soil tests to develop DRIS norms and evaluate their effectiveness in coastal Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) forests. DRIS norms for nitrogen, phosphorus, potassium, and calcium were developed using soil test and site index data from 72 soil series that commonly support Douglas-fir in western Washington. The norms were tested using soil test and stand basal area growth response data from 20 thinned and 30 unthinned N fertilizer test sites in coastal Washington and Oregon. Response to urea fertilizer in thinned stands averaged 34% and 43% for 224 and 448 kg N•ha−1, respectively, when N was identified as the most limiting nutrient. When N was not the most limiting nutrient, N response averaged 8% and 10% for 224 and 448 kg N•ha−1, respectively. Results were similar in unthinned stands and thinned stands, although response to fertilizer appeared to be slightly less in unthinned stands when N was the most limiting nutrient. DRIS correctly classified 25 of the 33 sites (76%) where N fertilizer increased growth by more than 15%. More importantly, 13 of the 17 (76%) sites that responded by less than 15% were correctly identified by DRIS. The results clearly indicate that N fertilizer response is dependent on the interactions (balance) between soil nutrients at a given site. Future soil diagnostic work needs to focus on techniques, like DRIS, that provide an assessment of these interactions.
Willow colonization of Rocky Mountain mires
Authors: Cottrell Tom R.
Published: March 2008

Salixplanifolia Pursh ssp. planifolia and Salixmonticola Bebb are the dominant willow species of Colorado Rocky Mountain willow carrs. Extensive field observations suggest that neither of these species is capable of sexual propagation under continuous sedge cover on peat soils. Growth experiments using willow stem cuttings in pots of saturated peat soil indicate that S. planifolia produces more root biomass (p = 0.0031) and shoot biomass (p = 0.0001) than S. monticola during one summer of growth. Male 5. planifolia and female S. monticola produce more dry-weight root (p = 0.0390) and shoot (p = 0.0442) biomass than their conspecific opposite sex. A species by sex by elevation interaction is significant for root biomass (p = 0.0360). The results are suggestive that these taxa have different regeneration niches. Asexual propagation driven by beaver activity is suggested as an explanation for the dominance of s. planifolia in mires and how this species colonizes vegetated peat soils. Beaver cut and store willow stems for a winter food source. This activity provides willow fragments for asexual colonization of mires.
Estimating ages of giant sequoias
Authors: Stephenson Nathan L. , Demetry Athena
Published: March 2008

When a tree's bole diameter exceeds 2 m, it is often impractical or impossible to determine its age directly and nondestructively, such as by counting or cross-dating rings on increment cores that sample the entire bole radius. We used ring measurements from complete stump cross sections of giant sequoia (Sequoiadendrongiganteum (Lindley) Buchholz) to develop a new method for estimating ages, which models age as a power function of bole radius. The value of the function's exponent varies from tree to tree and is most strongly related to the reciprocal of a tree's growth rate, as determined from increment cores that sample only the outer portion of the bole. For sequoia stumps up to 3200 years old and 6.5 m in diameter, our age estimates were within 10% of actual age 62% of the time, and within 25% of actual age 98% of the time, even when increment cores had sampled less than 20% of bole radius. This is a substantial improvement over previously published methods that estimate tree age from diameter alone, by assuming that basal area increment is constant through time, or by linear extrapolation of growth rates from the innermost portion of an increment core. The latter three methods are shown to be special cases of our more general approach.
Spatial and temporal variation in the Bight environment of developing Scots pine stands: the basis for a quick and efficient method of characterizing Bight
Authors: Messier Christian , Puttonen Pasi
Published: March 2008

Spatial and temporal variations in photosynthetic photon flux density (PPFD) at 1 m above the forest floor were measured under and between dominant pines and in 21- to 52-m2 gaps under developing Scots pine (Pinussylvestris L.) stands in southern Finland. For each stand, PPFD data were collected continuously every 10-s and then averaged for every 5-min period during 4-6 days under completely clear and overcast sky conditions. Measurements were made during 102 consecutive days within two different areas in each of 10 different Scots pine stands ranging in age from 7 to 105 years. Mean daily percent PPFD in the understory varied from 7.5% in the 20-year-old stands to 38% in the 7-year-old stands, and did not differ significantly between completely clear and overcast sky conditions. Mean daily percent PPFD did not vary significantly between the different sensor locations within closed pine stands, indicating that at high latitudes mean daily percent PPFD does not vary much spatially under closed Scots pine forests. Measurements of PPFD made at different periods during the day under clear sky conditions, one of the main approaches used in the literature, were not representative of the whole-day conditions. Two different results suggest that PPFD can be better characterized under completely overcast sky conditions. First, the 5-min percent PPFD in the understory was fairly constant between 06:00 and 20:00 for all stand ages under completely overcast sky conditions. Second, there was an almost perfect 1:1 relationship of the mean daily percent PPFD measured at 40 different locations in the 10 stands between clear and overcast sky conditions. These two results suggest that an instantaneous measure of percent PPFD obtained under completely overcast sky conditions is representative of the mean daily percent PPFD for both sky conditions. These results provide the basis for a quick and efficient method of estimating the mean daily percent PPFD in the understory of closed forests.
ANALYTICAL DESCRIPTION OF RECURRENCE PLOTS OF DYNAMICAL SYSTEMS WITH NONTRIVIAL RECURRENCES
Authors: ZOU Y. , THIEL M. , ROMANO M. C. , KURTHS J.
Published: March 2008

In this paper we study recurrence plots (RPs) for the simplest example of nontrivial recurrences, namely in the case of a quasiperiodic motion. This case can be still studied analytically and constitutes a link between simple periodic and more complicated chaotic dynamics. Since we deal with nontrivial recurrences, the size of the neighborhood ∊ to which the trajectory must recur, is larger than zero. This leads to a nonzero width of the lines, which we determine analytically for both periodic and quasiperiodic motion. The understanding of such microscopic structures is important for choosing an appropriate threshold ∊ to analyze experimental data by means of RPs.
OREGONATOR-BASED SIMULATION OF THE BELOUSOV–ZHABOTINSKII REACTION
Authors: CHOU MO-HONG , WEI HSIU-CHUAN , LIN YU-TUAN
Published: March 2008

Some observations are made on the Belousov–Zhabotinskii reaction simulated via the Field–Noyes model, also referred to as the Oregonator, and its modification. The simulation is performed with the aid of a cell-to-cell mapping for global analysis. Regarding the standard Oregonator, a two-dimension-like region in the three-dimensional phase space is detected showing the sensitive dependence of short-term ODE integrations on initial conditions. Trajectories with initial conditions closely located in this region may experience a phase lag if they eventually approach the same stable limit cycle connected with a subcritical Hopf bifurcation. When a flow term is added to the Oregonator, chaos can be brought about to mimic the experimental finding by suitably pleating the slow manifold. Coexistent attractors now may have a chaotic member and a fractal separatrix detected by the global analysis. The above mentioned sensitive region is found to play a significant role in shaping the pleating in order for chaos to happen in a manner analogous to the "screw-type" proposed by [Rössler, 1977] as one of the two prototypes for three-variable systems. Some relevant calculations of Lyapunov exponents, fractal dimensions and power spectra are also included.
SC-CNN BASED MULTIFUNCTION SIGNAL GENERATOR
Authors: KILIÇ RECAI
Published: March 2008

This paper presents a very versatile multifunction signal generator tool. The proposed generator is based on State Controlled Cellular Neural Network (SC-CNN) based Chua's circuit and it has two signal generation modes, namely CM (Chaos Mode) and FM (Function Mode). While the generator is able to produce nonlinear chaotic waveforms in Chaos Mode, it is also able to generate other classical sinusoidal, triangle and square waveforms in Function Mode. The proposed design idea has been validated through computer simulations and laboratory experiments. Future studies with the proposed generator tool will contribute to further developments in SC-CNN based engineering applications.
EXPONENTIAL CONVERGENCE OF CELLULAR NEURAL NETWORKS WITH CONTINUOUSLY DISTRIBUTED DELAYS
Authors: LIU BINGWEN , YUAN ZHAOHUI
Published: March 2008

In this paper the convergence behavior of delayed cellular neural networks without almost periodic coefficients are considered. Some sufficient conditions are established to ensure that all solutions of the networks converge exponentially to an almost periodic function, which are new, and also complement previously known results.
ON THE STABILIZATION OF PERIODIC ORBITS FOR DISCRETE TIME CHAOTIC SYSTEMS BY USING SCALAR FEEDBACK
Authors: MORGÜL ÖMER
Published: March 2008

In this paper we consider the stabilization problem of unstable periodic orbits of discrete time chaotic systems by using a scalar input. We use a simple periodic delayed feedback law and present some stability results. These results show that all hyperbolic periodic orbits as well as some nonhyperbolic periodic orbits can be stabilized with the proposed method by using a scalar input, provided that some controllability or observability conditions are satisfied. The stability proofs also lead to the possible feedback gains which achieve stabilization. We will present some simulation results as well.
CHAOTIC LIQUID SHAKER: DESIGN, IMPLEMENTATION AND APPLICATION
Authors: ZHANG ZHONG , CHEN GUANRONG
Published: March 2008

It has been argued that chaotic vibration provides the best possibility for achieving efficient and thorough mixing of fluids, by evoking complex and abundant perturbations into the original steady flows. In the last two decades, advances in the understanding of chaos theory and nonlinear-circuit technologies have led to favorable prospects to capitalize some features of chaos in liquid mixing applications. In this paper, a liquid mixing apparatus (an electromechanical shaker) based on the commonly used stirred tank model is introduced. The design and implementation of this liquid shaker, capable of working under the control of different kinds of signals, are reported. Constant-voltage signals, periodic signals and chaotic/hyperchaotic signals are applied to the impeller/tank velocity control mechanisms, exploring the efficacy of different perturbation schemes for liquid mixing. Comparable experiments are carried out to investigate the time consumption in sucrose dissolving processes and the dye dispersion homogeneity in visualizable mixing flows. The results of these experiments reveal that chaotic and hyperchaotic perturbations help enhance the liquid mixing efficiency and homogeneity quite significantly, yielding faster and more uniform results than all nonchaotic counterparts.
MOUNTAIN REDUCTION, BLOCK MATCHING, AND APPLICATIONS IN INTENSITY-MODULATED RADIATION THERAPY
Authors: CHEN DANNY Z. , HU XIAOBO S. , WANG CHAO , LUAN SHUANG , WU XIAODONG
Published: March 2008

In this paper, we present a new geometric algorithm for the 3-D static leaf sequencing (SLS) problem arising in intensity-modulated radiation therapy (IMRT), a modern cancer treatment technique. The treatment time and machine delivery error are two crucial factors for measuring the quality of a solution (i.e., a treatment plan) for the SLS problem. In the current clinical practice, physicians prefer to use treatment plans with the lowest possible amount of delivery error, and are also very concerned about the treatment time. Previous SLS methods in both the literature and commercial treatment planning systems either cannot minimize the error or achieve that only by using treatment plans which require a prolonged treatment time. In comparison, our new geometric algorithm is computationally efficient; more importantly, it guarantees that the output treatment plans have the lowest possible amount of delivery error, and the treatment time for the plans is significantly shorter. Our solution is based on a number of novel schemes and ideas (e.g., mountain reduction, block matching, profile-preserving cutting, etc) which may be of interest in their own right. Experimental results based on real medical data showed that our new algorithm runs fast and produces much better quality treatment plans than current commercial planning systems and well-known algorithms in medical literature.
A blended approach to active learning in a physiology laboratory-based subject facilitated by an e-learning component
Authors: Dantas Arianne M. , Kemm Robert E.
Published: March 2008

Learning via online activities (e-learning) was introduced to facilitate existing face-to-face teaching to encourage more effective student preparation and then informed participation in an undergraduate physiology laboratory-based course. Active learning was encouraged by hypothesis formation and predictions prior to classes, with opportunities for students to amend their e-learning submissions after classes. Automatic or tutor feedback was provided on student submissions. Evaluation of the course was conducted via student questionnaires, individual student interviews, and analysis of student marks in examinations and of the e-learning component. Student feedback on this entire subject in the university-wide quality of teaching survey was very high by University of Melbourne standards and most encouraging for the first implementation of such a curriculum modification. Results from further detailed surveys of student interactions and engagement and correlation analysis between student responses were also very supportive of the effectiveness of the course. There were no significant differences between examination marks in the new course with e-learning and the previous year without e-learning. However, there was a significant correlation between assessment of student e-learning work and their final examination mark. Correlation analysis between various survey responses helped interpret results and strengthened arguments for e-learning and suggested future improvements for student use of e-learning. This mode of e-learning used to support face-to-face learning activities in the laboratory can be adapted for other disciplines and may assist students in developing a greater appreciation and a deeper approach for learning from their practical class experiences.