bluuebunny/crossref_metadata_2025 huggingface dataset:
Activity of Meropenem with and without Ciprofloxacin and Colistin against
Pseudomonas aeruginosa
and
Acinetobacter baumannii
Authors: Pankuch Glenn A. , Lin Gengrong , Seifert Harald , Appelbaum Peter C.
Published: October 2007

Time-kill synergy studies showed that at 24 h, subinhibitory meropenem and ciprofloxacin concentrations of 0.06 to 128 and 0.03 to 32 μg/ml, respectively, showed synergy against 34/51
Pseudomonas aeruginosa
strains; subinhibitory concentrations of meropenem (0.06 to 8 μg/ml) and colistin (0.12 to 1 μg/ml) showed synergy against 13 isolates. Subinhibitory meropenem and ciprofloxacin concentrations of 0.25 to 2 and 0.12 to 16 μg/ml, respectively, showed synergy against 18/52
Acinetobacter baumannii
strains at 24 h. Subinhibitory meropenem and colistin concentrations of 0.03 to 64 and 0.06 to 8 μg/ml, respectively, showed synergy against 49 strains at 24 h.
Identification and Evaluation of a Highly Effective Fusion Inhibitor for Human Metapneumovirus
Authors: Deffrasnes Céline , Hamelin Marie-Ève , Prince Gregory A. , Boivin Guy
Published: October 2007

Human metapneumovirus (hMPV) can cause acute upper and lower respiratory tract infections that are particularly severe in young children, elderly subjects, and immunocompromised patients. To date, no treatments or vaccines are available for hMPV infections. Our objective was to assess the inhibitory potential of several peptides derived from the heptad repeat A and B (HRA and HRB) domains of the hMPV fusion protein. Nine candidate peptides were expressed in
Escherichia coli
or obtained synthetically and tested in vitro and in an animal model. Excellent in vitro inhibition of an hMPV strain of the A1 subgroup was obtained with five peptides, with 50% inhibitory concentrations ranging from 1.4 nM to 3.3 μM. One peptide, HRA2, displayed very potent activity against all four hMPV subgroups. It was also moderately active against human respiratory syncytial virus (strain A2) but displayed no activity against human parainfluenza virus type 3. BALB/c mice that received the HRA2 peptide and a lethal hMPV intranasal challenge simultaneously were completely protected from clinical symptoms and mortality. On day 5 postinfection, HRA2-treated mice had undetectable lung viral loads which were significantly less than those of untreated mice (3 × 10
4
50% tissue culture infective doses/lung). Pulmonary inflammation, levels of proinflammatory cytokines/chemokines (RANTES, gamma interferon, and monocyte chemoattractant protein 1) and airway obstruction were also significantly decreased in HRA2-treated mice. The results of this study demonstrate that potent antivirals can be derived from the hMPV fusion protein HR domains. Moreover, hMPV, compared to other paramyxoviruses and to the human immunodeficiency virus, seems to be more susceptible to HRA- than HRB-derived peptides.
Mechanisms by Which the G333D Mutation in Human Immunodeficiency Virus Type 1 Reverse Transcriptase Facilitates Dual Resistance to Zidovudine and Lamivudine
Authors: Zelina Shannon , Sheen Chih-Wei , Radzio Jessica , Mellors John W. , Sluis-Cremer Nicolas
Published: October 2007

Recent studies have identified a role for mutations in the connection and RNase H domains of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) resistance to nucleoside analog RT inhibitors (NRTI). To provide insight into the biochemical mechanism(s) involved, we investigated the effect of the G333D mutation in the connection domain of RT on resistance to zidovudine (AZT) and lamivudine (3TC) in enzymes that contain both M184V and thymidine analog mutations (TAMs; M41L, L210W, and T215Y). Our results from steady-state kinetic, pre-steady-state kinetic, and thermodynamic analyses indicate that G333D facilitates dual resistance to AZT and 3TC in two ways. First, in combination with M184V, G333D increased the ability of HIV-1 RT to effectively discriminate between the normal substrate dCTP and 3TC-triphosphate. Second, G333D enhanced the ability of RT containing TAMs and M184V to bind template/primer terminated by AZT-monophosphate (AZT-MP), thereby restoring ATP-mediated excision of AZT-MP under steady-state assay conditions. This study is the first to elucidate a molecular mechanism whereby a mutation in the connection domain of RT can affect NRTI susceptibility at the enzyme level.
Comparative Evaluation of the Inhibitory Activities of a Series of Pyrimidinedione Congeners That Inhibit Human Immunodeficiency Virus Types 1 and 2
Authors: Buckheit Robert W. , Hartman Tracy L. , Watson Karen M. , Chung Sun-Gan , Cho Eui-Hwan
Published: October 2007

Seventy-three analogs of SJ-3366 (1-(3-cyclopenten-1-ylmethyl)-5-ethyl-6-(3,5-dimethylbenzoyl)-2,4(1H,3H)-pyrimidinedione) were synthesized and comparatively evaluated for their ability to inhibit the replication of human immunodeficiency virus type 1 (HIV-1) and HIV-2 and for their ability to suppress virus entry and reverse transcription. These studies were performed to identify inhibitors with activity greater than that of the current lead molecule (SJ-3366) and to utilize structure-activity relationships (SAR) to define the chemical features of the pyrimidinedione congeners responsible for their efficacy, toxicity, and dual mechanism of action against HIV. The results of our SAR evaluations have demonstrated that the addition of the homocyclic moiety at the N-1 of the pyrimidinedione results in acquisition of the ability to inhibit virus entry and extends the range of action of the compounds to include HIV-2. In addition, the results demonstrate that analogs with a methyl linker between the homocyclic substitution and the N-1 of the pyrimidinedione had a greater number of highly active molecules than those analogs possessing ethyl linkers. Six molecules were identified with activity equivalent to or greater than that of SJ-3366, and five additional molecules with highly potent inhibition of reverse transcriptase and virus entry and possessing high efficacy against both HIV-1 and HIV-2 were identified. Six molecules exhibited significant inhibition of viruses with the highly problematic nonnucleoside reverse transcriptase inhibitor (NNRTI) resistance engendering amino acid change K103N in the reverse transcriptase. These evaluations indicate that a new class of NNRTIs has been identified and that these NNRTIs possess highly potent inhibition of HIV-1 with an extended range of action, which now includes HIV-2.
A DNA Fusion Vaccine Induces Bactericidal Antibodies to a Peptide Epitope from the PorA Porin of
Neisseria meningitidis
Authors: Zhu Delin , Williams Jeannette N. , Rice Jason , Stevenson Freda K. , Heckels John E. , Christodoulides Myron
Published: October 2007

An experimental DNA plasmid vaccine was developed based on a well-characterized and protective peptide epitope derived from a bacterial porin protein. For this study, we used the P1.16b serosubtype epitope, located in variable region (VR)2 in loop 4 of the PorA outer membrane (OM) porin from
Neisseria meningitidis
serogroup B strain MC58. A plasmid that encoded the entire loop (pPorAloop4) was prepared, as well as a fusion plasmid that encoded the loop in tandem with the fragment C (FrC) immunostimulatory sequence from tetanus toxin (pPorAloop4-FrC). The constructs were used for intramuscular immunization without exogenous adjuvant. Murine antisera raised to the pPorAloop4-FrC DNA fusion plasmid reacted significantly with OMs in enzyme-linked immunosorbent assay and with whole bacteria by immunofluorescence, whereas antisera raised to the pPorAloop4 DNA plasmid and to control plasmid showed little or no reactivity. Significantly, only the pPorALoop4-FrC plasmid induced bactericidal antibodies, demonstrating that the intrinsic immunostimulatory sequence was essential for inducing a protective immune response. The antibodies raised to the P1.16b pPorALoop4-FrC plasmid were serosubtype specific, showing no significant immunofluorescence reactivity or bactericidal activity against other PorA variants. These data provide proof of principle for a DNA fusion plasmid strategy as a novel approach to preparing vaccines based on defined, protective epitopes.
Modulation of the Host Cell Proteome by the Intracellular Apicomplexan ParasiteToxoplasma gondii
Authors: Nelson M. M. , Jones A. R. , Carmen J. C. , Sinai A. P. , Burchmore R. , Wastling J. M.
Published: October 2007

To investigate how intracellular parasites manipulate their host cell environment at the molecular level, we undertook a quantitative proteomic study of cells following infection with the apicomplexan parasiteToxoplasma gondii. Using conventional two-dimensional electrophoresis, difference gel electrophoresis (DIGE), and mass spectrometry, we identified host proteins that were consistently modulated in expression following infection. We detected modification of protein expression in key metabolic pathways, including glycolysis, lipid and sterol metabolism, mitosis, apoptosis, and structural-protein expression, suggestive of global reprogramming of cell metabolism by the parasite. Many of the differentially expressed proteins had not been previously implicated in the response to the parasite, while others provide important corroborative protein evidence for previously proposed hypotheses of pathogen-cell interactions. Significantly, over one-third of all modulated proteins were mitochondrial, and this was further investigated by DIGE analysis of a mitochondrion-enriched preparation from infected cells. Comparison of our proteomic data with previous transcriptional studies suggested that a complex relationship exits between transcription and protein expression that may be partly explained by posttranslational modifications of proteins and revealed the importance of investigating protein changes when interpreting transcriptional data. To investigate this further, we used phosphatase treatment and DIGE to demonstrate changes in the phosphorylation states of several key proteins following infection. Overall, our findings indicate that the host cell proteome responds in a dramatic way toT. gondiiinvasion, in terms of both protein expression changes and protein modifications, and reveal a complex and intimate molecular relationship between host and parasite.
NonpathogenicEscherichia coliStrain Nissle 1917 Inhibits Signal Transduction in Intestinal Epithelial Cells
Authors: Kamada Nobuhiko , Maeda Kenichi , Inoue Nagamu , Hisamatsu Tadakazu , Okamoto Susumu , Hong Kyong Su , Yamada Takaya , Watanabe Noriaki , Tsuchimoto Kanji , Ogata Haruhiko , Hibi Toshifumi
Published: October 2007

Although the probioticEscherichia colistrain Nissle 1917 has been used for the treatment of inflammatory bowel diseases, the precise mechanisms of action of this strain remain unclear. In the present study, we estimated the anti-inflammatory effect ofE.coliNissle 1917 on inflammatory responses in vitro to determine the suppressive mechanism of Nissle 1917 on the inflammatory process. To determine the effect ofE.coliNissle 1917, the human colonic epithelial cell line HCT15 was incubated with or withoutE.coliNissle 1917 or another nonpathogenicE.colistrain, K-12, and then tumor necrosis factor alpha (TNF-α)-induced interleukin-8 (IL-8) production from HCT15 cells was assessed. Enzyme-linked immunosorbent assays and real-time quantitative PCR showed that Nissle 1917 treatment suppressed TNF-α-induced IL-8 transcription and production. In addition, results from luciferase assays indicated that Nissle 1917 inhibited IL-8 promoter activity. On the other hand, these anti-inflammatory effects were not seen withE.coliK-12. In addition, heat-killed Nissle 1917 or its genomic DNA did not have this anti-inflammatory effect. Surprisingly, Nissle 1917 did not affect IL-8 transactivation pathways, such as NF-κB activation, nuclear translocation, and DNA binding, or even activation of other transcriptional factors. Furthermore, it also became evident that Nissle 1917 induced the anti-inflammatory effect without contact to epithelial cells. In conclusion, these data indicate that the nonpathogenicE.colistrain Nissle 1917 expresses a direct anti-inflammatory activity on human epithelial cells via a secreted factor which suppresses TNF-α-induced IL-8 transactivation through mechanisms different from NF-κB inhibition.
Correlations among measures of quality in HIV care in the United States: cross sectional study
Authors: Wilson Ira B , Landon Bruce E , Marsden Peter V , Hirschhorn Lisa R , McInnes Keith , Ding Lin , Cleary Paul D
Published: October 2007

Objective
To determine whether a selected set of indicators can represent a single overall quality construct.

Design
Cross sectional study of data abstracted during an evaluation of an initiative to improve quality of care for people with HIV.

Setting
69 sites in 30 states.

Data sources
Medical records of 9020 patients.

Main outcome measures
Adjusted performance rates at site level for eight measures of quality of care specific to HIV and a site level summary performance score (the number of measures for which the site was in the top quarter of the distribution).

Results
Of 28 site level correlations between measures, two were greater than 0.40, two were between 0.30 and 0.39, four were between 0.20 and 0.29, and the 20 remaining were all less than 0.20. One site was in the top quarter for seven measures, but no sites were in the top quarter for six or eight of the measures. Across the eight quality measures, sites were in the top quarter no more often than predicted by a chance (binomial) distribution.

Conclusions
The quality suggested by one measured indicator cannot necessarily be generalised to unmeasured indicators, even if this might be expected for clinical or other reasons.
Quantification of Douglas-fir growth losses caused by western spruce budworm defoliation using stem analysis
Authors: Alfaro R. I. , Thomson A. J. , Sickle G. A. Van
Published: October 2007

Periodic growth and volume losses in Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees in one stand defoliated four times in their lifetime by western spruce budworm (Choristoneuraoccidentalis (Freeman)) are reported. Losses were calculated by comparing periodic growth for the years of reduced ring increment with potential growth estimated using the IMPACT growth loss program. Proportional losses in stem radius and cross-sectional area remained approximately constant or declined slightly from tree top to base; losses differed at all stem levels among the infestations. Average gross volume losses per tree relative to the potential volume the trees should have reached at the end of each loss period were 17, 15, 8, and 13% for the 1920's, 1940's, 1950's, and 1970's infestations, respectively. In the last infestation, losses ranged from 9% in trees defoliated from 1 to 50%, to 18% in trees defoliated 91–100%. Cumulative tree volume losses, calculated by adjusting growth during all loss periods to their potential values, were estimated to be 44% of the potential volume the trees should have reached by 1977 had the trees never been defoliated. On a per hectare basis, the 1970's infestation in this stand caused an estimated 60 m3 (18%) loss, comprising 40 m3 (12%) owing to tree mortality and 20 m3 (6%) of growth deficit in the surviving trees.
Planting site and genotype affect black walnut seedling development more than nursery environment
Authors: Williams Robert D. , Rink George , Funk David T.
Published: October 2007

A black walnut (Juglansnigra L.) provenance–progeny test was established on four widely separated sites, with seedlings grown at two nurseries to contrast the effects of site, seedling size, and genotype. Five years after establishment, site and genotype effects continued to be large while the nursery effect, although statistically significant, was diminishing in importance. Therefore, seedling size resulting from cultural nursery manipulation is not as important as proper geographic seed origin or site selection.
Relationships between CO2 evolution from soil, substrate temperature, and substrate moisture in four mature forest types in interior Alaska
Authors: Schlentner Robert E. , Cleve Keith Van
Published: October 2007

A soda lime technique was used to measure CO2 evolution at the soil surface in four mature forest types (aspen (Populustremuloides Michx.), paper birch (Betulapapyrifera Marsh.), black spruce (Piceamariana (Mill.) B.S.P.), and white spruce (Piceaglauca (Moeneh) Voss)) in interior Alaska. Surface temperature, 15-cm depth temperature, and soil moisture were measured concurrently with CO2 evolution. Accumulated CO2 evolution ranged from 1315 to 1654 g CO2•m−2 for the period May 1 – September 30 in 1981 and 1982 in the four stands. Data were used to develop three-dimensional response surfaces and test mathematical models of respiration in relation to substrate temperature and moisture. GRESP, a biologically based model, provided a fairly accurate simulation of the seasonal course of respiration as a function of substrate temperature and moisture. In an attempt to better define the observed response surface trends, a best-fit equation model, BRESP, was formulated. BRESP includes the moisture portion of the GRESP equation, and an altered temperature equation which more adequately defines the upper and lower thresholds of respiration in relation to substrate temperature. GRESP and BRESP each produced similar r2 values; however, higher order polynomial equations gave a better-fit model. The weakest area of all models for simulating seasonal trends was during the periods of peak respiration in June.
The influence of shelter and the hypothetical effect of fire severity on the postfire establishment of conifers from seed
Authors: Thomas P. A. , Wein Ross W.
Published: October 2007

Surface-charred organic matter is a common but unfavourable postfire seedbed in eastern Canada. Slatted screens providing 0, 25, 50, and 75% cover were used to shelter 1-m2 charred plots from direct sunlight. Plots were sown with four conifer species. Jack pine (Pinnsbanksiana Lamb.) established abundantly on all plots and dominated on unsheltered areas. As shelter increased, eastern white pine (Pinusstrobus L.), and eventually balsam fir (Abiesbalsamea (L.) Mill.) and black spruce (Piceamariana (Mill.) B.S.P.) increased in number. Thus, the size and composition of the seedling community depended upon the amount of shelter given. To test whether postfire herbaceous and shrub vegetation could have a similar effect, seeds were sown on pairs of charred 1-m2 plots. Vegetation was removed weekly from one plot of each pair. Removal of vegetation decreased the establishment of balsam fir and black spruce but not red pine (Pinusresinosa Ait.). It was concluded that, during the first growing season, changes in vegetation cover produce changes in establishment similar to those found using slatted screens. Increasing fire severity (organic matter consumption) may reduce the postfire vegetation cover. A hypothetical model is presented, linking the establishment of the above five species to fire severity.
Managerial finance for silvicultural systems
Authors: Rideout Doug
Published: October 2007

Recent advances in the economic theory of uneven-aged forest management are integrated and expressed in terms of cash flow analysis for managerial purposes. Silvicultural systems are exemplified by shelterwood and selection systems. The financial methodology developed for shelterwood and selection systems is based on the concept of a long-term managed forest value. The managed forest value which represents the long-term value of the forest under optimal management, is largely independant of the initial stand condition. The managed forest value is analagous with, but not equal to, forest land value as defined in the 1849 Faustmann model. Financial methodology is first developed for shelterwood. Selection management is subsequently discussed and shown by example to be of similar financial structure.
White spruce (Piceaglauca) flowering in response to spray application of gibberellin A4/7
Authors: Cecich Robert A.
Published: October 2007

Experiments were conducted on three populations of white spruce (Piceaglauca (Moench) Voss) to determine if calendar dates could be used as guidelines to spray gibberellin A4/7 in an Aromox–ethanol solution to increase flowering and to determine if early flushing (EF) and late flushing (LF) clones, sprayed on the same dates, responded differently. Spraying from July 8 to September 9 was ineffective, but spraying from May 7 to July 1 gave a significant response. Elongating shoots sprayed from May 13 to June 3 produced significantly more ovulate and staminate strobili than did elongating shoots sprayed from June 10 to July 1, and both produced significantly more than the control. Gibberellin A4/7 significantly increased production of ovulate and staminate strobili in the EF and LF clones that were sprayed only from June 2 to June 30. LF clones produced significantly more ovulate strobili than the EF clones, but there was no significant difference between them in staminate strobilus production. The studies demonstrated that the timing of gibberellin A4/7 spray application affects the flowering response in white spruce.
Estimating Douglas-fir fine root biomass and production from living bark and starch
Authors: Vogt K. A. , Vogt D. J. , Moore E. E. , Littke W. , Grier C. C. , Leney L.
Published: October 2007

A potential indirect technique for determining fine root biomass and production is reported for Douglas-fir. Present data show a direct correlation between the starch content of a 1 cm wide band of living bark at breast height per hectare and fine root biomass per hectare (r2 = 0.85).
Inoculation of Douglas-fir and western hemlock roots with naturally infected inocula of Phellinusweirii
Authors: Kellas J. D.
Published: October 2007

A method is described using Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) root segments naturally infected with Phellinusweirii (Murr.) Gilb. to inoculate healthy roots of Douglas-fir and western hemlock (Tsugaheterophylla (Raf.) Sarg.) trees. Growth of ectotrophic mycelium from inoculum onto host roots was used as an indicator of the likely success of inoculation. Inoculated roots of both Douglas-fir and western hemlock showed a similar degree of ectotrophic mycelial development following P. weirii inoculation. Ectotrophic mycelia developed more frequently onto host roots from inoculations made in February or August than in late May (resulting in 87, 100, and 25% mycelial development on host roots, respectively). Necrosis of bark was observed on 53% of the roots showing mycelial development and P. weirii was isolated from 38% of these roots.
Methodological considerations in the analysis of forest disturbance history
Authors: Lorimer Craig G.
Published: October 2007

A number of nondestructive techniques for analyzing the timing, frequency, and magnitude of natural disturbances in forest stands are discussed in this paper. Intensive age determination of trees is desirable for reconstructing forest disturbance history, but age distribution alone is not always a sufficient basis for a disturbance chronology. Frequently all-aged forests have undergone severe past disturbance which cannot be readily identified from the distribution of trees among age-classes. Radial growth patterns provide more direct evidence of past canopy tree deaths. In cases where a large sample of tree ages and growth records is not feasible, structural attributes of forests can provide valuable supplementary evidence. Evidence of the effects of disturbance history and age structure on diameter distributions is examined, and principles for valid interpretation proposed. Crown area distributions and diameter distributions of nonsuppressed trees potentially appear to be more reliable structural indicators of past canopy disturbance than simple size distributions. For regional studies of disturbance frequency, random dispersal of medium to large plots across large landscape units is recommended as a sample design.
The theory and use of two fire history models
Authors: Johnson E. A. , Wagner C. E. Van
Published: October 2007

The objective of this paper is to explain the distributions, assumptions, interpretations, and relationships of the two compatible, stochastic models of fire history: the negative exponential and the Weibull. For each model the "fire interval" and "time-sinee-fire" distributions are given. Both models apply to homogenous stationary stochastic processes. The negative exponential states that the instantaneous fire hazard rate is constant for all stand ages. The Weibull states that the instantaneous fire hazard rate increases with stand age when the shape parameter is > 1 (the negative exponential is a special ease of the Weibull when shape = 1). An empirical method is given for separating from an observed fire history distribution, the pre- and post-fire suppression distributions. Four relationships are derived from the models and defined per study region (per stand): (i) the fire cycle (average fire interval), (ii) the annual percent burned area (fire frequency), (iii) the average age of the vegetation (average prospective life-time), and (iv) the renewal rate.
Changes in biomass components through stand development in wave-regenerated balsam fir forests
Authors: Sprugel Douglas G.
Published: October 2007

Available data on the wave-regenerated Abiesbalsamea forests of the northeastern United States are synthesized into a model (BALSAM) which predicts changes in total and component biomass through the disturbance–regeneration cycle. Measured decay rates seem to imply a higher mean forest floor mass than is actually observed, so several alterations were made in the initial model to make it predict forest floor mass correctly. With or without these changes, forest floor mass decreases for about 12 years after disturbance, largely owing to low levels of litterfall in the early stages of stand development. Because changes in living biomass and dead bole mass through the disturbance cycle roughly cancel each other out, net ecosystem productivity closely parallels these litterfall-driven changes in the forest floor. Throughout the disturbance–regeneration cycle, the forest floor is derived primarily from woody tissue and its decay products, with foliage-derived material making up less than 25% of the total forest floor mass.
Prospects and progress in conifer biotechnology
Authors: Dunstan David I.
Published: October 2007

Forests are a highly significant component of Canada's landscape and economy. They are subjected to an ever increasing burden through the pressures of competition and the environment. Canada's forests must be restocked with phenotypically superior, genetically improved trees that will mature to provide a competitive product for the future. Traditional improvement and silvicultural practices, assisted by developing biotechnologies, will be needed to fulfil this responsibility. This discussion specifically highlights recent developments in the emerging field of conifer biotechnology and indicates some of the applications to which they may eventually be put.
Decay and stain 10 years later in aspen suckers subjected to scarification at age 3
Authors: Basham J. T.
Published: October 2007

A trembling aspen (Populustremuloides Michx.) sucker stand was scarified at age 3 to benefit subsequently planted white spruce (Piceaglauca (Moench) Voss). Survivors were examined 4, 6, and 10 years after treatment. The effects of scarification on aspen stem growth, and on external and internal quality of both roots and stems, were assessed at those times. Damage inflicted on the parent root system significantly reduced stem growth after scarification. Ten years after scarification normal height growth had resumed, but diameter growth was still slightly slower than that of unscarified suckers. Scarification wounds on the root systems were common and frequently associated with root and root-collar decay. Both the root systems and stems of scarified suckers had significantly more internal decay and stain than those of unscarified suckers. Stem wounds apparently caused by scarification were present on approximately 75% of the survivors, and accounted for most of the extra defect in scarified stems. The extent of advanced stem decay was closely correlated with the severity of stem wounds. Several basidiomycete fungi known to cause advanced butt and stem decay in mature aspen in Ontario were isolated from decay within the root systems and stems of scarified suckers. In unscarified suckers these basidiomycetes were not isolated or were isolated much less frequently. The large numbers of surviving suckers, their nearly normal growth rates, and the relatively small size of the planted spruce 10 years after scarification indicate that the aspen will develop into well-stocked, harvestable stands. However, a high proportion of the aspen that survive scarification will likely be more susceptible than unscarified aspen to windthrow or breakage. The scarified trees will likely be of lower quality as well, because the incidence and extent of decay in the root systems and lower stems are comparatively high.
Long-term response of understory vegetation to stand density in Picea-Tsuga forests
Authors: Alaback Paul B. , Herman F. R.
Published: October 2007

The 17-year response of understory vegetation to forest thinning experiments was examined in two study sites on the central Oregon coast to determine the role of overstory species composition and stand density on forest succession. At 6 months, no significant difference in shrub, herb, and moss species composition or abundance was detected between the two study sites. Seventeen years after treatment, however, the Piceasitchensis (Bong.) Carr. site had much less vegetation cover and diversity than the Tsugaheterophylla (Raf.) Sarg. site. Overall response of most vascular species to thinning was insignificant because of their high variability in the medium and heavy treatments. Carpet-forming mosses were consistent in increasing their percent ground cover following thinning in the Picea site, and were the only species group to increase cover relative to initial conditions. Tsuga saplings were significantly more abundant under Picea canopies than under Tsuga canopies, probably because of the increased openness of Picea canopies. The increased abundance of saplings at both sites, particularly following heavy thinning, led to a two-layered overstory canopy and relatively less shrub and herb cover and diversity. Except for ferns, most plants that persisted had animal-dispersed seed. Thinning had little effect on the loss of understory species relative to the controls. Increases in diversity with thinning occurred primarily as the result of increased invasion by shade-tolerant species. Regardless of thinning treatment, only one-third or less of the original plant cover was maintained on study plots at stand age 30 years. Early thinnings without subsequent treatments are unlikely to maintain stable herb and shrub populations in forest types where the understory would otherwise be eliminated during the intermediate stages of stand development.
Family and family × nitrogen interaction effects on juvenile growth of PrunusSerotina
Authors: Stanton Brian J. , Gerhold Henry D.
Published: October 2007

Regeneration of black cherry (Prunusserotina Ehrh.) on the Allegheny Plateau is often inadequate, but in some cases it may be improved through fertilization and planting. Thirty open-pollinated families of select phenotypes from a clonal orchard and natural stands were evaluated using four rates of nitrogen at three sites to determine the magnitude of family variation in current annual height increment and height at age 2 and the extent of family × nitrogen interactions. Significant nitrogen effects were observed in the variation in both the 2nd year's annual height increment and total height at one site. A 27% increase in current annual increment was associated with the application of nitrogen. Family variation in height was evident at all sites; the range between the tallest and shortest families varied between 46 and 66% of the respective plantation height. Family × nitrogen interactions were never an important source of variation. Implications for a black cherry artificial regeneration program are discussed.
Variation in biomass production, moisture content, and specific gravity in some North American willows (Salix L.)
Authors: Mosseler A. , Zsuffa L. , Stoehr M. U. , Kenney W. A.
Published: October 2007

Biomass production and quality in seedlings and coppices of Salixamygdaloides Anderss., S. eriocephala Michx., S. exigua Nutt., and S. lucida Muhl. were investigated in a full-sib family test. Between 65 and 77% of the variation in plant biomass was due to species, while less than 5% was due to families. Approximately 39% of the variation in moisture content and 37% of the variation in specific gravity was due to species differences, while only 3 and 14%, respectively, was due to families. Salixeriocephala produced the highest yields, with an average 1-year coppice production of almost 1 kg/plant (dry matter) and had the lowest moisture content and highest specific gravity of the four species. There was a strong positive correlation between seedling and coppice productivity for all species, with S. eriocephala and S. lucida producing the most vigorous regrowth from coppice.
Cultural treatment of young yellow birch (Betulaalleghaniensis Britton) stands: tree classification and stand structure
Authors: Ouellet Denis , Zarnovican Richard
Published: October 2007

The IUFRO classification criteria were applied to yellow birch stems in a lower pole stand located in the Saint-Zacharie experimental forest. Mensuration data were analyzed using the classification criteria. The results show that the stand in which yellow birch predominates has a relatively homogeneous diametrical and vertical structure. Social differentiation and some species hierarchy are evident even at this early stage. Mensuration data analyses reveal the discriminatory value of several IUFRO criteria (height class, development class, silvicultural class); other criteria (evolutive trend class, technological standard class) are more difficult to apply. The suggestion is made that two indices (ht/dbh ratio, crown clearance) would facilitate tree classification in young hardwood stands.
Exchange rates, Canadian lumber imports, and United States prices: a time-series analysis
Authors: Buongiorno Joseph , Chavas Jean-Paul , Uusivuori Jussi
Published: October 2007

Softwood lumber imports by the United States from Canada more than doubled during the past 10 years. The objective of this paper was to investigate two possible reasons for this change: (i) the increase in value of the U.S. dollar relative to the Canadian dollar, and (ii) the rise in the price of softwood lumber in the United States. The method used was time-series analysis, leading to measures of feedback and long-term multipliers between imports, exchange rate, and U.S. price. The results, based on monthly data from January 1974 to January 1986, suggested that 68% of the rise in Canadian imports during this period was due to the rise in the price of softwood lumber in the United States. The exchange rate, however, was not found to have a significant effect on imports. The findings also indicate that the increase in imports has not led to a decline in the price received by U.S. producers.
Nucleotide sequence of the carboxy-terminal portion of a lodgepole pine actin gene
Authors: Kenny J. R. , Dancik B. P. , Florence L. Z. , Nargang F. E.
Published: October 2007

We have determined the nucleotide sequence of the carboxy-terminal portion of an actin gene (PAc1-A) isolated from Pinuscontorta var. latifolia (Engelm.). Pairwise comparisons of both nucleotide and deduced amino acid sequences were made among PAc1-A, the soybean actins SAc3 and SAc1, maize actin MAc1, chicken β-actin, and yeast β-actin. Of the other actins SAc3 was most similar to the PAc1-A amino acid sequence (91.3% identity) and yeast actin the least similar (78.3% identity). The intron in PAc1-A is present at the same location as the third intron found in MAc1, SAc1, and SAc3 actin genes. This conservation of intron position is unusual when compared with nonplant actin genes.
Seasonal and long-term responses of host trees to microbial associates of the pine engraver, Ipspini
Authors: Raffa Kenneth F. , Smalley Eugene B.
Published: October 2007

Within-season responses of Pinusresinosa and Pinusbanksiana to fungi vectored by the pine engraver, Ipspini, are strongly influenced by the month of inoculation. The seasonal pattern is a characteristic of the host-fungus interaction, rather than being indicative of either host-or fungal-specific properties alone. The most consistent trend was that early season inoculation resulted in more rapid lesion formation in sapwood than in phloem and that this difference declined as the growing season progressed. Prior inoculation had no effect on necrotic lesion formation. Inoculated trees were examined for three growing seasons. No significant damage related to treatment occurred to either P. resinosa or P. banksiana during this interval. However, Ceratocystisips persisted in living hosts for a longer period than did Ceratocystisnigrocarpa and showed signs of radial and vertical progression throughout the first and beginning of the second growing season. This was especially true in P. resinosa, the host in which the short-term studies revealed the lower lesion growth rate. There was no lesion formation during the third season. Inoculated fungi could be reisolated from within but not outside the resulting lesion.
Effets de l'élagage sur la résistance électrique cambiale de la tige de jeunes Sapins baumiers
Authors: Gagnon Robert R. , Chabot Michel , Pineau Marius
Published: October 2007

In the spring of 1985, 125 young balsam fir trees (Abiesbalsamea (L.) Mill.) originating from advanced regeneration following a clear-cut in 1970 were pruned to live crown ratios of 0.6, 0.4, 0.2 and 0.0 as compared with control trees which had naturally developped a live crown ratio of 0.8. Subsequently, the cambial electrical resistance of these trees was measured at breast height 17 times between June and October. Ten days after pruning, there was a decrease in cambial electrical resistance. Relating these results to factors influencing the movement of water through the tree leads to a better understanding of the physiological significance of tree stem cambial electrical resistance.
GENERATING ALL CIRCULAR SHIFTS BY CONTEXT-FREE GRAMMARS IN GREIBACH NORMAL FORM
Authors: ASVELD PETER R. J.
Published: October 2007

For each alphabet Σn = {a1,a2,…,an}, linearly ordered by a1 < a2 < ⋯ < an, let Cn be the language of circular or cyclic shifts over Σn, i.e., Cn = {a1a2 ⋯ an-1an, a2a3 ⋯ ana1,…,ana1 ⋯ an-2an-1}. We study a few families of context-free grammars Gn (n ≥1) in Greibach normal form such that Gn generates Cn. The members of these grammar families are investigated with respect to the following descriptional complexity measures: the number of nonterminals ν(n), the number of rules π(n) and the number of leftmost derivations δ(n) of Gn. As in the case of Chomsky normal form, these ν, π and δ are functions bounded by low-degree polynomials. However, the question whether there exists a family of grammars that is minimal w. r. t. all these measures remains open.
LINKS
Authors: DREWES FRANK
Published: October 2007

We define the notion of links, thus generalizing the chain-code, turtle geometry, and collage formalisms. As links can be concatenated, link grammars can be defined in a similar way as chain-code grammars. Context-free link grammars are shown to be strictly more powerful than both context-free chain-code grammars and context-free collage grammars. Moreover, we study the generalization obtained by extending the formalism with the brackets known from the turtle geometry.
CLASSES OF TREE LANGUAGES DETERMINED BY CLASSES OF MONOIDS
Authors: GÉCSEG FERENC
Published: October 2007

In this paper finite state recognizers are considered as unary tree recognizers with unary operational symbols. We introduce translation recognizers of a tree recognizer, which are finite state recognizers whose operations are the elementary translations of the underlying algebra of the considered tree recognizer. In terms of translation recognizers we give general conditions under which a class of recognizable tree languages with a given property can be determined by a class of monoids determining the class of string languages having the same property.
CONTEXT-FREE GRAMMARS WITH LINKED NONTERMINALS
Authors: KLEIN ANDREAS , KUTRIB MARTIN
Published: October 2007

We introduce a new type of finite copying parallel rewriting system, i. e., grammars with linked nonterminals, which extend the generative capacity of context-free grammars. They can be thought of as having sentential forms where some instances of a nonterminal may be linked. The context-free-like productions replace a nonterminal together with its connected instances. New links are only established between symbols of the derived subforms. A natural limitation is to bound the degree of synchronous rewriting. We present an infinite degree hierarchy of separated language families with the property that degree one characterizes the family of regular and degree two the family of context-free languages. Furthermore, the hierarchy is a refinement of the known hierarchy of finite copying rewriting systems. Several closure properties known from equivalent systems are summarized.
AMBIGUITY BY RESTARTING AUTOMATA
Authors: MRÁZ FRANTIŠEK , PLÁTEK MARTIN , JURDZIŃSKI TOMASZ
Published: October 2007

Restarting automata can be considered as a machine model as well as regulated rewriting systems. We introduce a measure of ambiguity for restarting automata which recognizes a language as a projection of its characteristic language (containing also auxiliary—non-input—symbols) into its input alphabet. Based on this measure we define an ambiguity measure of languages. This measure can be considered as a measure of non-determinism of languages. We show that there is an infinite hierarchy with respect to the degree of ambiguity even inside linear languages and that there are linear languages with a linear ambiguity.
COMPUTING MORPHISMS BY SPIKING NEURALPSYSTEMS
Authors: PĂUN GHEORGHE , PÉREZ-JIMÉNEZ MARIO J. , ROZENBERG GRZEGORZ
Published: October 2007

We continue the study of the spiking neural P systems considered as transducers of binary strings or binary infinite sequences, and we investigate their ability to compute morphisms. The class of computed morphisms is rather restricted: length preserving or erasing, and the so-called 2-block morphisms can be computed; however, non-erasing non-length-preserving morphisms cannot be computed.
STATE COMPLEXITY OF ADDITIVE WEIGHTED FINITE AUTOMATA
Authors: SALOMAA KAI , SCHOFIELD PAUL
Published: October 2007

It is known that the neighborhood of a regular language with respect to an additive distance is regular. We introduce an additive weighted finite automaton model that provides a conceptually simple way to reprove this result. We consider the state complexity of converting additive weighted finite automata to deterministic finite automata. As our main result we establish a tight upper bound for the state complexity of the conversion.
PREFIX-FREE ŁUKASIEWICZ LANGUAGES
Authors: STAIGER LUDWIG
Published: October 2007

Generalised Łukasiewicz languages are simply described languages having good information-theoretic properties. An especially desirable property is the one of being a prefix code. This paper addresses the question under which conditions a generalised Łukasiewicz language is a prefix code. Moreover, an upper bound on the delay of decipherability of a generalised Łukasiewicz language is derived.
Transcranial Ultrasound in Acute Stroke: From Diagnosis to Therapy
Authors: Molina Carlos A. , Alexandrov Andrei V.
Published: October 2007

In the last few years, several studies have improved our knowledge and understanding of the dynamic nature of the recanalization process during stroke thrombolysis. Transcranial Doppler ultrasound provides a unique opportunity to assess several aspects of clot dissolution by means of continuous monitoring of recanalization during and after administration of tissue plasminogen activator. This approach allows us to evaluate at the patient’s bedside and in real time the beginning, timing, speed and degree of artery reopening, as well as to document reocclusion after successful recanalization. Moreover, the simultaneous clinical assessment during transcranial Doppler monitoring allows correlation of the hemodynamic changes with the clinical course and outcome. Experimental studies have shown that ultrasound (US)-accelerated thrombolysis may be further enhanced by administration of microbubbles (MBs). Low-frequency US with high power has been demonstrated to produce cavitation and fluid motion in the thrombus. The MBs, by acting as cavitation nuclei, lower the amount of energy needed for cavitation. Application of high-acoustic-pressure US has been shown to induce nonlinear oscillations of MBs, leading to a continuous absorption of energy until the bubbles explode, releasing the absorbed energy. A multicenter randomized phase II trial of MB-enhanced thrombolysis in acute stroke is under way.
Applicability of Biomarkers in Ischemic Stroke
Authors: Castellanos Mar , Serena Joaquín
Published: October 2007

Cerebral ischemia results in the activation of a cascade of molecular events as a result of which several substances with the potential characteristics of biomarkers are released into the peripheral blood. Although still in the research phase, the analysis of these biomarkers in the serum has proved to be useful for stroke diagnosis, as well as for the prediction of the evolution of the ischemic lesion and the clinical prognosis. In fact, the feasibility and applicability of a panel of biomarkers for the diagnosis of stroke has recently been tested. Biomarkers of excitotoxicity, inflammation and oxidative stress have been demonstrated as being useful in the prediction of ischemic lesion enlargement and secondary neurological deterioration. On the other hand, biomarkers of endothelial damage have been shown to be especially helpful in the prediction of hemorrhagic transformation of the ischemic lesion, both spontaneously and after the administration of thrombolytic therapy, as well as in the prediction of brain edema with the secondary development of malignant middle-cerebral-artery infarction. Moreover, coagulation and fibrinolytic-cascade markers have been reported as being correlated with the recanalization rate after the administration of thrombolysis, and they might therefore be useful in estimating the effectiveness of thrombolytic therapy. However, for these biomarkers to become applicable to routine clinical practice, faster tests to perform the analyses are required and further studies must be undertaken to validate and generalize the results.
Noninvasive Angiography (Magnetic Resonance and Computed Tomography) in the Diagnosis of Ischemic Cerebrovascular Disease
Authors: Schellinger Peter D. , Richter Gregor , Köhrmann Martin , Dörfler Arnd
Published: October 2007

Noninvasive diagnostic imaging of the craniocervical and intracranial vasculature is a domain of computed tomography angiography (CTA), magnetic resonance angiography (MRA) and Doppler/duplex ultrasound, the latter not being the topic of this presentation. We give a methodological background for both, CTA and MRA, followed by a critical appraisal of both imaging modalities in the diagnosis of ischemic cerebrovascular disease. The contribution of noninvasive vascular imaging to vascular malformations (including aneurysms, fistulas and cerebral-vein thrombosis) is beyond the scope of this paper and therefore not covered.