bluuebunny/crossref_metadata_2025 huggingface dataset:
A “HOWFARLESS” option to increase efficiency of homogeneous phantom calculations with DOSXYZnrc
Authors: Walters B. R. B. , Kawrakow I.
Published: October 2007

This paper describes a “HOWFARLESS” transport option, which has been added to DOSXYZnrc to increase the efficiency of beam commissioning calculations in homogeneous phantoms. The algorithm speeds up charged particle transport by only considering the distance to the extreme outer boundaries of the phantom, thus eliminating the need to stop at voxel boundaries. Dose is deposited by approximating the total curved charged particle steps by two straight‐line steps joined at a hinge point. Good agreement with normal simulations is achieved at all beam energies and for all practical maximum step lengths with a 1:1 mixture of approximations based on the initial position/direction of the particle and on its final position/direction. Use of the “HOWFARLESS” option in phantom calculations for 6 and photon beams ( and fields) from BEAMnrc‐simulated accelerators increases the efficiency at the optimum photon splitting number by a factor of 2.9–5.4 when the exact EGSnrc boundary crossing algorithm (BCA) is used and by 51%–89% when the faster PRESTA‐I BCA is employed. The efficiency gain due to the “HOWFARLESS” transport option increases with increasing beam energy and decreases with increasing field/dose voxel size. Efficiency improvement is greater when the efficiency of the particle source itself is not a factor, and in such cases the “HOWFARLESS” option improves the DOSXYZnrc efficiency by up to a factor of 13.1 (exact BCA) or 3.5 (PRESTA‐I BCA) for photon beams, and up to a factor of 17.2 (exact BCA) or 5.2 (PRESTA‐I BCA) for electron beams.
On‐line quality assurance of rotational radiotherapy treatment delivery by means of a 2D ion chamber array and the Octavius phantom
Authors: Van Esch Ann , Clermont Christian , Devillers Magali , Iori Mauro , Huyskens Dominique P.
Published: October 2007

For routine pretreatment verification of innovative treatment techniques such as (intensity modulated) dynamic arc therapy and helical TomoTherapy, an on‐line and reliable method would be highly desirable. The present solution proposed by TomoTherapy, Inc. (Madison, WI) relies on film dosimetry in combination with up to two simultaneous ion chamber point dose measurements. A new method is proposed using a 2D ion chamber array (Seven29, PTW, Freiburg, Germany) inserted in a dedicated octagonal phantom, called Octavius. The octagonal shape allows easy positioning for measurements in multiple planes. The directional dependence of the response of the detector was primarily investigated on a dual energy (6 and ) Clinac 21EX (Varian Medical Systems, Palo Alto, CA) as no fixed angle incidences can be calculated in the Hi‐Art TPS of TomoTherapy. The array was irradiated from different gantry angles and with different arc deliveries, and the dose distributions at the level of the detector were calculated with the AAA (Analytical Anisotropic Algorithm) photon dose calculation algorithm implemented in Eclipse (Varian). For validation on the TomoTherapy unit, rotational treatments were generated, and dose distributions were calculated with the Hi‐Art TPS. Multiple cylindrical ion chamber measurements were used to cross‐check the dose calculation and dose delivery in Octavius in the absence of the 2D array. To compensate for the directional dependence of the 2D array, additional prototypes of Octavius were manufactured with built‐in cylindrically symmetric compensation cavities. When using the Octavius phantom with a compensation cavity, measurements with an accuracy comparable to that of single ion chambers can be achieved. The complete Octavius solution for quality assurance of rotational treatments consists of: The 2D array, two octagonal phantoms (with and without compensation layer), an insert for nine cylindrical ion chambers, and a set of inserts of various tissue equivalent materials of different densities. The combination of the 2D array with the Octavius phantom proved to be a fast and reliable method for pretreatment verification of rotational treatments. Quality control of TomoTherapy patients was reduced to a total of per patient.
Optimization of image acquisition techniques for dual‐energy imaging of the chest
Authors: Shkumat N. A. , Siewerdsen J. H. , Dhanantwari A. C. , Williams D. B. , Richard S. , Paul N. S. , Yorkston J. , Van Metter R.
Published: October 2007

Experimental and theoretical studies were conducted to determine optimal acquisition techniques for a prototype dual‐energy (DE) chest imaging system. Technique factors investigated included the selection of added x‐ray filtration, kVp pair, and the allocation of dose between low‐ and high‐energy projections, with total dose equal to or less than that of a conventional chest radiograph. Optima were computed to maximize lung nodule detectability as characterized by the signal‐difference‐to‐noise ratio (SDNR) in DE chest images. Optimal beam filtration was determined by cascaded systems analysis of DE image SDNR for filter selections across the periodic table , demonstrating the importance of differential filtration between low‐ and high‐kVp projections and suggesting optimal high‐kVp filters in the range . For example, added filtration of , , , and to the high‐kVp beam provided optimal (and nearly equivalent) soft‐tissue SDNR. Optimal kVp pair and dose allocation were investigated using a chest phantom presenting simulated lung nodules and ribs for thin, average, and thick body habitus. Low‐ and high‐energy techniques ranged from and , respectively, with peak soft‐tissue SDNR achieved at for all patient thicknesses and all levels of imaging dose. A strong dependence on the kVp of the low‐energy projection was observed. Optimal allocation of dose between low‐ and high‐energy projections was such that of the total dose was delivered by the low‐kVp projection, exhibiting a fairly weak dependence on kVp pair and dose. The results have guided the implementation of a prototype DE imaging system for imaging trials in early‐stage lung nodule detection and diagnosis.
Field‐size dependence of doses of therapeutic carbon beams
Authors: Kusano Yohsuke , Kanai Tatsuaki , Yonai Shunsuke , Komori Masataka , Ikeda Noritoshi , Tachikawa Yuji , Ito Atsushi , Uchida Hirohisa
Published: October 2007

To estimate the physical dose at the center of spread‐out Bragg peaks (SOBP) for various conditions of the irradiation system, a semiempirical approach was applied. The dose at the center of the SOBP depends on the field size because of large‐angle scattering particles in the water phantom. For a small field of , the dose was reduced to 99.2%, 97.5%, and 96.5% of the dose used for the open field in the case of 290, 350, and carbon beams, respectively. Based on the three‐Gaussian form of the lateral dose distributions of the carbon pencil beam, which has previously been shown to be effective for describing scattered carbon beams, we reconstructed the dose distributions of the SOBP beam. The reconstructed lateral dose distribution reproduced the measured lateral dose distributions very well. The field‐size dependencies calculated using the reconstructed lateral dose distribution of the therapeutic carbon beam agreed with the measured dose dependency very well. The reconstructed beam was also used for irregularly shaped fields. The resultant dose distribution agreed with the measured dose distribution. The reconstructed beams were found to be applicable to the treatment‐planning system.
Resolution and noise trade‐off analysis for volumetric CT
Authors: Li Baojun , Avinash Gopal B. , Hsieh Jiang
Published: October 2007

Until recently, most studies addressing the trade‐off between spatial resolution and quantum noise were performed in the context of single‐slice CT. In this study, we extend the theoretical framework of previous works to volumetric CT and further extend it by taking into account the actual shapes of the preferred reconstruction kernels. In the experimental study, we also attempt to explore a three‐dimensional approach for spatial resolution measurement, as opposed to the conventional two‐dimensional approaches that were widely adopted in previously published studies. By scanning a finite‐sized sphere phantom, the MTF was measured from the edge profile along the spherical surface. Cases of different resolutions (and noise levels) were generated by adjusting the reconstruction kernel. To reduce bias, the total photon fluxes were matched: , , and per gantry rotation. All data sets were reconstructed using a modified FDK algorithm under the same condition: Scan field‐of‐view , and slice . The theoretical analysis indicated that the variance of noise is proportional to power of the spatial resolution. Our experimental results supported this conclusion by showing the relationship is 4.6th (helical) or 5th (axial) power.
Quantitative coronary angiography using image recovery techniques for background estimation in unsubtracted images
Authors: Wong Jerry T. , Kamyar Farzad , Molloi Sabee
Published: October 2007

Densitometry measurements have been performed previously using subtracted images. However, digital subtraction angiography (DSA) in coronary angiography is highly susceptible to misregistration artifacts due to the temporal separation of background and target images. Misregistration artifacts due to respiration and patient motion occur frequently, and organ motion is unavoidable. Quantitative densitometric techniques would be more clinically feasible if they could be implemented using unsubtracted images. The goal of this study is to evaluate image recovery techniques for densitometry measurements using unsubtracted images. A humanoid phantom and eight swine were used to evaluate the accuracy and precision of the following image recovery techniques: Local averaging (LA), morphological filtering (MF), linear interpolation (LI), and curvature‐driven diffusion image inpainting (CDD). Images of iodinated vessel phantoms placed over the heart of the humanoid phantom or swine were acquired. In addition, coronary angiograms were obtained after power injections of a nonionic iodinated contrast solution in an in vivo swine study. Background signals were estimated and removed with LA, MF, LI, and CDD. Iodine masses in the vessel phantoms were quantified and compared to known amounts. Moreover, the total iodine in left anterior descending arteries was measured and compared with DSA measurements. In the humanoid phantom study, the average root mean square errors associated with quantifying iodine mass using LA and MF were approximately 6% and 9%, respectively. The corresponding average root mean square errors associated with quantifying iodine mass using LI and CDD were both approximately 3%. In the in vivo swine study, the root mean square errors associated with quantifying iodine in the vessel phantoms with LA and MF were approximately 5% and 12%, respectively. The corresponding average root mean square errors using LI and CDD were both 3%. The standard deviations in the differences between measured iodine mass in left anterior descending arteries using DSA and LA, MF, LI, or CDD were calculated. The standard deviations in the DSA‐LA and DSA‐MF differences (both ) were approximately a factor of 3 greater than that of the DSA‐LI and DSA‐CDD differences (both ). Local averaging and morphological filtering were considered inadequate for use in quantitative densitometry. Linear interpolation and curvature‐driven diffusion image inpainting were found to be effective techniques for use with densitometry in quantifying iodine mass in vitro and in vivo. They can be used with unsubtracted images to estimate background anatomical signals and obtain accurate densitometry results. The high level of accuracy and precision in quantification associated with using LI and CDD suggests the potential of these techniques in applications where background mask images are difficult to obtain, such as lumen volume and blood flow quantification using coronary arteriography.
Accelerating reconstruction of reference digital tomosynthesis using graphics hardware
Authors: Yan Hui , Ren Lei , Godfrey Devon J. , Yin Fang‐Fang
Published: October 2007

The successful implementation of digital tomosynthesis (DTS) for on‐board image guided radiation therapy (IGRT) requires fast DTS image reconstruction. Both target and reference DTS image sets are required to support an image registration application for IGRT. Target images are usually DTS image sets reconstructed from on‐board projections, which can be accomplished quickly using the conventional filtered backprojection algorithm. Reference images are DTS image sets reconstructed from digitally reconstructed radiographs (DRRs) previously generated from conventional planning CT data. Generating a set of DRRs from planning CT is relatively slow using the conventional ray‐casting algorithm. In order to facilitate DTS reconstruction within a clinically acceptable period of time, we implemented a high performance DRR reconstruction algorithm on a graphics processing unit of commercial PC graphics hardware. The performance of this new algorithm was evaluated and compared with that which is achieved using the conventional software‐based ray‐casting algorithm. DTS images were reconstructed from DRRs previously generated by both hardware and software algorithms. On average, the DRR reconstruction efficiency using the hardware method is improved by a factor of 67 over the software method. The image quality of the DRRs was comparable to those generated using the software‐based ray‐casting algorithm. Accelerated DRR reconstruction significantly reduces the overall time required to produce a set of reference DTS images from planning CT and makes this technique clinically practical for target localization for radiation therapy.
Effects of frequency characteristics of reverberation time on listener envelopment
Authors: Morimoto Masayuki , Jinya Munehiro , Nakagawa Koichi
Published: October 2007

Spatial impression perceived in a listening space comprises at least two components: one is auditory (apparent) source width (ASW) and the other is listener envelopment (LEV). Both ASW and LEV are affected not only by temporal but also by spatial structures of reflections. It has been clarified that ASW for symphony music is significantly affected by low-frequency components of source signals and reflections, but not by their high-frequency components. The objective of this work is to investigate whether LEV is affected by the frequency characteristics of source signals and reverberation sounds, which are known to contribute to the creation of LEV. In this study, three experiments were performed to clarify the effects of reverberation time (RT) and its frequency characteristics on LEV. In contrast to the case of ASW, the experimental results show that RTs both at high and low frequencies affect LEV.
Analysis and modeling of piano sustain-pedal effects
Authors: Lehtonen Heidi-Maria , Penttinen Henri , Rauhala Jukka , Välimäki Vesa
Published: October 2007

This paper describes the main features of the sustain-pedal effect in the piano through signal analysis and presents an algorithm for simulating the effect. The sustain pedal is found to increase the decay time of partials in the middle range of the keyboard, but this effect is not observed in the case of the bass and treble tones. The amplitude beating characteristics of piano tones are measured with and without the sustain pedal engaged, and amplitude envelopes of partial overtone decay are estimated and displayed. It is found that the usage of the sustain pedal introduces interesting distortions of the two-stage decay. The string register response was investigated by removing partials from recorded tones; it was observed that as the string register is free to vibrate, the amount of sympathetic vibrations is increased. The synthesis algorithm, which simulates the string register, is based on 12 string models that correspond to the lowest tones of the piano. The algorithm has been tested with recorded piano tones without the sustain pedal. The objective and subjective results show that the algorithm is able to approximately reproduce the main features of the sustain-pedal effect.
A robust noniterative method for obtaining scattering strengths of multiply scattering point targets
Authors: Chen Xudong , Zhong Yu
Published: October 2007

A noniterative method based on the least squares technique is presented in this letter to obtain the scattering strengths of multiply scattering point targets. Benefiting from the least squares’ optimization property, this new method achieves a good estimation of the scattering strengths. Compared with the noniterative method proposed in a recent paper [E. A. Marengo and F. K. Gruber “Noniterative analytical formula for inverse scattering of multiply scattering point targets,” J. Acoust. Soc. Am. 120, 3782–3788 (2006)], the new method produces more accurate results in the presence of noise.
Short range scattering of the fundamental shear horizontal guided wave mode normally incident at a through-thickness crack in an isotropic plate
Authors: Rajagopal P. , Lowe M. J. S.
Published: October 2007

Interaction of the fundamental shear horizontal mode with through-thickness cracks in an isotropic plate is studied in the context of low frequency array imaging for ultrasonic guided wave nondestructive evaluation with improved resolution. Circular wave fronts are used and the symmetric case where a line from the wave source bisects the crack face normally is considered. Finite element simulations are employed to obtain trends subject to analytical and experimental validation. The influence of the crack length and of the location of source and measurement positions on the specular reflection from the crack face is first examined. These studies show that low frequency short range scattering is strongly affected by diffraction phenomena, leading to focusing of energy by the crack in the backscatter direction. Study of the diffraction from the crack edges reveals contributions due to a direct diffraction at the edges and multiple reverberations across the crack length. A simple diffraction model is shown to adequately represent cracks up to moderate lengths, providing an easy means of estimating the far field of the waves. The presence of multiple diffraction components is quantitatively established and surface waves on the crack face are identified as equivalent to low frequency symmetric modes of rectangular ridge waveguides.
Spectral and temporal cues for phoneme recognition in noise
Authors: Xu Li , Zheng Yunfang
Published: October 2007

Cochlear implant users receive limited spectral and temporal information. Their speech recognition deteriorates dramatically in noise. The aim of the present study was to determine the relative contributions of spectral and temporal cues to speech recognition in noise. Spectral information was manipulated by varying the number of channels from 2 to 32 in a noise-excited vocoder. Temporal information was manipulated by varying the low-pass cutoff frequency of the envelope extractor from 1to512Hz. Ten normal-hearing, native speakers of English participated in tests of phoneme recognition using vocoder processed consonants and vowels under three conditions (quiet, and +6 and 0dB signal-to-noise ratios). The number of channels required for vowel-recognition performance to plateau increased from 12 in quiet to 16–24 in the two noise conditions. However, for consonant recognition, no further improvement in performance was evident when the number of channels was ⩾12 in any of the three conditions. The contribution of temporal cues for phoneme recognition showed a similar pattern in both quiet and noise conditions. Similar to the quiet conditions, there was a trade-off between temporal and spectral cues for phoneme recognition in noise.
Voriconazole Inhibits Melanization in
Cryptococcus neoformans
Authors: Martinez Luis R. , Ntiamoah Patricia , Gácser Attila , Casadevall Arturo , Nosanchuk Joshua D.
Published: October 2007

Voriconazole is a triazole antifungal drug that inhibits ergosterol synthesis and has broad activity against yeast and molds. While studying the interaction of voriconazole and
Cryptococcus neoformans
, we noted that cells grown in the presence of subinhibitory concentrations of voriconazole reduced melanin pigmentation. We investigated this effect systematically by assessing melanin production in the presence of voriconazole, amphotericin B, caspofungin, itraconazole, and fluconazole. Only voriconazole impeded the formation of melanin at subinhibitory concentrations. Voriconazole did not affect the autopolymerization of
l
-dopa, and 0.5 MIC of voriconazole did affect the gene expression of
C. neoformans
. However, voriconazole inhibited the capacity of laccase to catalyze the formation of melanin. Hence, voriconazole affects melanization in
C. neoformans
by interacting directly with laccase, which may increase the efficacy of this potent antifungal against certain pigmented fungi.
Safety and Pharmacokinetics of GSK364735, a Human Immunodeficiency Virus Type 1 Integrase Inhibitor, following Single and Repeated Administration in Healthy Adult Subjects
Authors: Reddy Y. Sunila , Min Sherene S. , Borland Julie , Song Ivy , Lin Jiang , Palleja Sandra , Symonds William T.
Published: October 2007

GSK364735 is a human immunodeficiency virus (HIV) integrase strand transfer inhibitor with potent in vitro antiviral activity. This study was a double-blind, randomized, placebo-controlled, dose escalation, phase I study to assess single- and repeated-dose safety, tolerability, pharmacokinetics (PK), and food effect of GSK364735 in healthy subjects. In part A, three alternating cohorts of 10 subjects (8 receiving the active drug and 2 receiving a placebo) received single doses of 50 to 400 mg while fasting or 200 mg and 400 mg coadministered with food. In part B, five cohorts received repeated doses of 100 to 600 mg daily coadministered with food for 8 days. Safety was assessed throughout the study. Serial blood samples were analyzed for GSK364735 plasma concentrations using a validated high-performance liquid chromatography-tandem mass spectrometry assay. PK parameters were estimated using noncompartmental methods. Seventy-nine (30 in part A and 49 in part B) subjects were enrolled and received GSK364735 or placebo. GSK364735 was readily absorbed following oral dose administration, with the maximum concentration achieved between 0.75 to 5.0 h postdose. GSK364735 exposure increased less than dose proportionally, demonstrated wide variability, and appeared to reach a plateau at 100- to 200-mg doses. Food increased GSK364735 exposure by 28 to 91%. GSK364735 was safe and well tolerated after single- and repeated-dose administration. No serious or severe adverse events (AEs) or AEs leading to withdrawal and few drug-related AEs were reported. Despite solubility-limited absorption, GSK364735 exceeded therapeutic trough concentrations for the majority of doses studied. The PK and safety profile supported the continued investigation of GSK364735 in HIV-infected subjects.
Autophagy during Proliferation and Encystation in the Protozoan ParasiteEntamoeba invadens
Authors: Picazarri Karina , Nakada-Tsukui Kumiko , Nozaki Tomoyoshi
Published: October 2007

Autophagy is one of the three systems responsible for the degradation of cytosolic proteins and organelles. Autophagy has been implicated in the stress response to starvation, antigen cross-presentation, the defense against invading bacteria and viruses, differentiation, and development.Saccharomyces cerevisiaeAtg8 and its mammalian ortholog, LC3, play an essential role in autophagy. The intestinal protozoan parasiteEntamoeba histolyticaand a related reptilian species,Entamoeba invadens, possess the Atg8 conjugation system, consisting of Atg8, Atg4, Atg3, and Atg7, but lack the Atg5-to-Atg12 conjugation system. Immunofluorescence imaging revealed that polymorphic Atg8-associated structures emerged in the logarithmic growth phase and decreased in the stationary phase and also increased in the early phase of encystation inE. invadens. Immunoblot analysis showed that the increase in phosphatidylethanolamine-conjugated membrane-associated Atg8 was also accompanied by the emergence of Atg8-associated structures during the proliferation and differentiation mentioned above. Specific inhibitors of class I and III phosphatidylinositol 3-kinases simultaneously inhibited both the growth of trophozoites and autophagy and also both encystation and autophagy inE. invadens. These results suggest that the core machinery for autophagy is conserved and plays an important role during proliferation and differentiation inEntamoeba.
Macrophage-Mediated but Gamma Interferon-Independent Innate Immune Responses Control the Primary Wave ofPlasmodium yoeliiParasitemia
Authors: Couper Kevin N. , Blount Daniel G. , Hafalla Julius C. R. , van Rooijen Nico , de Souza J. Brian , Riley Eleanor M.
Published: October 2007

In most models of blood-stage malaria infection, proinflammatory immune responses are required for control of infection and elimination of parasites. We hypothesized therefore that the fulminant infections caused in mice by the lethal strain ofPlasmodium yoelii(17XL) might be due to failure to activate a sufficient inflammatory response. Here we have compared the adaptive CD4+T-cell and innate immune response toP. yoelii17XL with that induced by the self-resolving, nonlethal strain ofP. yoelii, 17X(NL). During the first 7 to 9 days of infection, splenic effector CD4+T-cell responses were similar in mice with lethal and nonlethal infections with similar levels of activation in vivo and equivalent proliferation in vitro following mitogenic stimulation. Nonspecific T-cell hyporesponsiveness was observed at similar levels during both infections and was due, in part, to suppression mediated by CD11b+cells. Importantly, however, RAG−/−mice were able to control the initial growth phase of nonlethalP. yoeliiinfection as effectively as wild-type mice, indicating that T cells and/or B cells play little, if any, role in control of the primary peak of parasitemia. Somewhat unexpectedly, we could find no clear role for either NK cells or gamma interferon (IFN-γ) in controlling primaryP. yoeliiinfection. In contrast, depletion of monocytes/macrophages exacerbated parasite growth and anemia during both lethal and nonlethal acuteP. yoeliiinfections, indicating that there is an IFN-γ-, NK cell-, and T-cell-independent pathway for induction of effector macrophages during acute malaria infection.
Basidiocarp development in Calocera cornea
Authors: Kennedy Lorene L.
Published: October 2007

The development of the basidiocarp of Calocera cornea in the natural and cultural environments is described. The structural unit is a narrow, unmodified hypha with the capacity for pigment and gel formation. In the basidiocarp the hyphae become organized into a central zone of compact, parallel hyphae, a median zone of interwoven hyphae with numerous spaces containing gelatinous material, and an outer zone composed of bifurcate basidia each bearing two basidiospores.Primordia and basidiocarps show rapid growth with marked sensitivity to relative humidity and sporulation frequently takes place before basidiocarp development is complete. Short periods of rapid growth alternate with long periods of inactivity during which the formation of fungal gel and carotenoid pigments probably aids in survival.
Tryptophan synthase: partial purification and some properties of the B-protein subunit from pea plants (Pisum sativum cv. Alaska)
Authors: Chen James , Boll W. G.
Published: October 2007

A method was developed for partial purification of the B-protein of tryptophan synthase (EC 4.2.1.20) from pea plants. The enzyme was purified 28-fold with about 21% recovery. The purification procedure removed both A-protein activity, and denatured A-protein, from the B-protein. The B-protein is unstable and activity was not preserved by either dithiothreitol, mercaptoethanol, or L-cysteine. These sulfhydryl compounds were inhibitory at relatively low concentrations. Both pyridoxal phosphate and glycerol preserved the activity to some extent. Glycerol itself was inhibitory. However, when enzyme was stored with 25% glycerol in the cold the activity actually increased within the first 24 h. The enzyme is most stable as a suspension in ammonium sulfate solution. The partially purified B-protein, in the absence of A-protein, catalyzed the condensation of indole and serine to tryptophan at an appreciable rate. Pyridoxal phosphate was required for maximal activity while both pyridoxine phosphate and pyridoxamine phosphate were inactive in the system. The molecular weight of the B-protein was estimated to be about 101 000, which is close to that of the B-protein subunit of Escherichia coli. Differences in properties between bacterial, tobacco, and pea TSase are discussed.
Genera coelomycetarum. III. Pestalozziella
Authors: Raj T. R. Nag , Kendrick Bryce
Published: October 2007

Four species are included in Pestalozziella Sacc. & Ell., P. andersonii Ell. & Ev., P. artocarpi sp. nov., P. parva Nag Raj, and P. subsessilis Sacc. & Ell. Six species and a variety earlier described in or transferred to Pestalozziella are excluded or considered as of doubtful status in the genus. Coma gen. nov., type species C. circularis (Cooke & Mass.) comb. nov. (≡ Pestalozziella circularis Cooke & Mass.) is described. Robillarda depazeoides (Welw. & Curr.) Sacc. appears to be congeneric with Pestalozziella.
A leaf spot polymorphism in Collinsia grandiflora (Scrophulariaceae)
Authors: Griffiths A. J. F. , Krause Gerda , Ganders Fred R.
Published: October 2007

A polymorphism for leaf spots has been described for populations of Collinsia grandiflora in southwestern British Columbia. The spotted morphs have been found mainly on the Vancouver Island Coast between Miracle Beach and Crofton. There is considerable variation in the spotted class. Most evident is the distinction between heavy and faint morphs. Genetic studies have demonstrated that heavy spotting is due to a single dominant gene, that the heavy-spotting system is genetically distinct from that for faint spotting and that the heavy-spotting system maintains its simple Mendelian inheritance pattern even in the presence of the faint-spotting determinants. The precise, genetic determination for faint spotting is uncertain but several models are consistent with the data. The reason for the existence of the polymorphism is not known.
The taxonomic status of Timmia sibirica
Authors: Horton Diana G.
Published: October 2007

A critical study of the differentiating features of the North American populations of Timmia sibirica Lindb. et Arnell and T. norvegica Zett. reveals that populations with structure intermediate between these two taxa occur. Although from widespread localities, the intermediate specimens seem limited in number and T. sibirica and T. norvegica quite commnonly occur in mixed populations with no evidence of any intergradation. Therefore, it is concluded that the two taxa ought to be regarded as distinct species. The taxonomically important character-states of upper leaf cells and costa of T. sibirica. T. norvegica, and of the intermediate populations are illustrated with scanning elecron micrographs. The habitat of T. sibirica, like that of T. norvegica, is invariably on strongly calcareous substrates adjacent to waterfalls, along streams, or in low-lying tundra. The North American distribution of T. sibirica is mapped, including previously unreported localities as far south as 51° N in the Canadian Rocky Mountains.
A 12 000 year palynological record of temperature and precipitation trends in southwestern British Columbia
Authors: Mathewes Rolf W. , Heusser Linda E.
Published: October 2007

Transfer functions for converting pollen frequencies to estimates of mean July temperature and mean annual precipitation were applied to fossil pollen data from a sediment core in Marion Lake. The paleotemperature curve shows low July temperatures near 14 °C at the base of the core at about 12 000 before present (B.P.), rising rapidly between 10 400 B.P. and 10 000 B.P. to maximum values slightly above 16 °C. Maximum temperatures cluster between 10 000 B.P. and approximately 7500 B.P., declining steadily thereafter until 6000 B.P. Little change is apparent from 6000 B.P. to the present. The reconstructed precipitation curve also shows a three-part zonation, with moderately high values between 12 000 and 10 400 B.P. dropping rapidly to minimum Holocene values between 10 000 and 7500 B.P. Precipitation rises to modern levels near the Mazama ash bed. The informal term "early Holocene xerothermic interval" is applied to the pre-Mazama interval of maximum temperatures and minimum precipitation.The late-glacial age at the base of the core is confirmed by a new radiocarbon date of 11 920 ± 245 years B.P. (I-6857) on lodgepole pine needles screened from the basal clays.
Aerial biomass distribution in an undisturbed and disturbed subarctic bog
Authors: Sims R. A. , Stewart J. M.
Published: October 2007

During powerline construction, a portion of a wooded (Picea mariana) peat plateau in northern Manitoba was stripped of surface vegetation. Seven years later, aerial biomass of plants recolonizing the surface of the disturbed area was estimated to be 2098 kg ha−1, only 26.4% of the undisturbed portion's aerial biomass of 7939 kg ha−1.Tree biomass represented 28.7% of the aboveground biomass of the wooded plateau. The relative proportions of photosynthetic phytomass increased from 17% in the wooded to 53% in the disturbed area. Major ericaceous species (Ledum groenlandicum, Chamaedaphne calyculata, and Kalmia polifolia) responded after disturbance by increasing reproductive effort and the ratio of photosynthetic to woody tissue.Permafrost subsidence in the disturbed portion was not evident in the period since vegetation removal, although surface erosion of peat was visible and could be expected to increase in the next several years.
Facteurs influant sur le processus d'établissement de thalles monozoospores chez Phytophthora infestans
Authors: Grand-Pernot Françoise Le
Published: October 2007

Studies of different stages of germination of zoospores until the establishment of colonies showed that each stage is differently affected by external agents. The first stage of encystment was shown to be heavily dependent on the environment; an early transfer of the zoospores from a liquid to a solid medium resulted in a higher percentage of encystment. The second stage, on the other hand, which is the growth of the germ tube, practically always occurred without specific nutritive requirements. The last stage, colony establishment, was more successful when germinated cysts were transferred to new media. It was evident that at each stage the presence of bacteria could make cloning difficult. A method which favours cloning by reducing bacterial proliferation is described. By using this method, cloning in this study was 60% successful.
Nuclear behavior and clarification of the spore stages of Uromyces koae
Authors: Gardner Donald E.
Published: October 2007

Recent observations showed that Uromyces koae Arthur in Stevens teliospores did not produce typical basidia or basidio-spores. The present study reveals that teliospores produced long germ tubes that are differentiated into wide proximal and narrow distal portions separated by a vesiclelike swelling. One or two extensive branches, each morphologically resembling the main tube, developed from individual germ tube cells. Nuclear staining revealed a single, presumably diploid nucleus in mature teliospores. One or more probable mitotic divisions in the main germ tube provided a diploid nucleus for each branch and for the main tube itself. Meiotic division of each nucleus produced a series of four smaller nuclei in the narrow portion of each branch and the main tube. The germ tubes may be modified basidia and serve as infectious hyphae in place of basidiospores.A formerly undescribed spore type associated with the teliospores is recognized as uredinial. This investigation shows that the life cycle of U. koae probably consists of four distinct stages, each on Acacia koa: the spermatial associated with the aecial on hypertrophied shoots, and the uredinial and telial together in discrete leaf pustules.
Effets physiologiques de la benzyladénine sur Lemna minor I. Influence sur la composition lipidique
Authors: Bérubé R. , Beaumont G. , Grenier G.
Published: October 2007

Doses from 0.002 to 2.0 ppm of benzyladenine (BA) increased the water content in 15-day-old plants of Lemna minor L. However, a concentration of 5.0 ppm decreased it. The total esterified fatty acid content increased up to 2.0 ppm and decreased at 5.0 ppm, compared with controls. The BA increased the percentages of total palmitic and α-linolenic acids and decreased the percentage of total linoleic acid, mainly for higher doses. At 2.0 and 5.0 ppm of BA, the proportions of phospholipids increased strongly as compared with galactolipids (especially the diacylgalactosylglycerol) and total neutral lipids. In phosphatidylcholine, phosphatidylethanolamine, and phosphotidylinositol, the α-linolenic acid content exhibited a marked increase at the expense of linoleic acid of these phospholipids. The percentage of α-linolenic acid in diacylgalactosylglycerol remained constant in the presence of BA, but it decreased in diacyldigalactosylglycerol. At concentrations of 2.0 and 5.0 ppm, the α-linolenic acid content of total neutral lipids increased greatly. The modifications observed in the lipid composition of L. minor, at 2.0 and 5.0 ppm in BA, suggest that the cell membranes (particularly those of chloroplasts) and their functions may be altered by these high doses of cytokinin.
Endophytic fungi in evergreen shrubs in western Oregon: A preliminary study
Authors: Petrini Orlando , Stone Jeffrey , Carroll Fanny E.
Published: October 2007

Endophytic fungi were isolated from five species of broad-leaved evergreen shrubs from 16 sites in western Oregon. Rates of infection were 76% for Mahonia nervosa, 44% for Arctostaphylos uva-ursi, 37% for Gaultheria shallon, 29% for Mahonia aquifolium, and 25% for Umbellularia californica. Incidence of leaf infections by more than one fungal taxon was 20–56%, 72–90% of which had only two infections. Rates of overall infection were higher in samples taken from densely wooded sites than in samples taken from more open sites. A pattern of species dominance is seen where the most common endophyte of a given host is isolated less frequently from other hosts; less commonly isolated endophytes appear to be less host specific. The most commonly isolated endophytes include Phyllosticta pyrolae on A. uva-ursi and G. shallon, Leptothyrium berberidis on M. nervosa, Septogloeum sp. on M. nervosa and U. californica, and Phomopsis sp., predominantly on M. aquifolium, but present on all hosts. Some of the fungi isolated from evergreen shrubs in this study were previously isolated from conifer needles; however, most represent new records.
Growth and sporulation in vitro of Cercospora apii, Cercospora arachidicola, Cercospora kikuchii, and other species of Cercospora
Authors: El-Gholl N. E. , Alfieri Jr. S. A. , Ridings W. H. , Schoulties C. L.
Published: October 2007

Cercospora apii Fres., Cercospora arachidicola Hori, and Cercospora kikuchii (Matsumoto & Tomoyasu) Gardn. were single spored, and the resultant colonies were characterized. All isolates of C. arachidicola were morphologically identical, whereas those of C. apii and C. kikuchii were either smooth or had radial folds. Variability in sporulation was also evident. Multiple-point inoculation of culture media in plates with conidia helped to overcome variability in the amount of conidial production. Maximum sporulation was obtained at 4 days with C. apii and C. kikuchii, and from 7 to 10 days with C. arachidicola. Single-point inoculation of a V-8 culture medium in plates from peripheral dark mycelial growth in potato dextrose agar (PDA) culture resulted in increased sporulation by C. kikuchii. Sporulation of C. kikuchii was maintained throughout a 15-month study by selective subculturing; however, conidial production decreased over time. A total of 15 other species of Cercospora sporulated within a week following a V-8 inoculation of culture medium in plates with mycelial agar blocks.
The genus Aporpium and two additional poroid fungi
Authors: Setoff Edson C. , Ryvarden Leif
Published: October 2007

The genus Aporpium is defined and descriptions given for four known species, as well as two other collections. Of the latter, Polystictus subreflexus Lloyd is found to have cruciate septate basidia and collection Dumont PA-84 from Panama is described as a Poria infected by the tremellaceous fungus Basidiodendron eyrei (Wakef.) Luck-Allen.
A phenolic–taxometric study of Medicago (Leguminosae)
Authors: Classen D. , Nozzolillo C. , Small E.
Published: October 2007

Phenolics from dried leaf tissue of 47 species of Medicago were examined using two-dimensional chromatography on polyamide plates. A few samples from the closely related genera Melilotus and Trigonella were also studied. Compounds tentatively identified as cyanidin, quercetin, kaempferol, luteolin, apigenin, chrysoeriol, tricin, and coumestrol were found. Proanthocyanidins were not detected in the leaf tissue of any of the species. Apigenin was found in all species of Medicago except M. cretacea but not in the one species of Melilotus or the two of Trigonella studied. Two additional compounds as yet unidentified were also restricted to Medicago. All of the phenolics were detected as aglycones with the possible exceptions of glucuronides and C-glycosides which are strongly resistant to hydrolysis. Data for the phenolic compounds were subjected to numerical taxonomic analysis. The single species of Melilotus and the two species of Trigonella were dramatically different from Medicago in their phenolic composition. A number of controversial species placed in Medicago by some taxonomists, and in Trigonella by others, proved to have phenolic profiles much like Medicago and quite unlike the species of Trigonella examined. The annual species comprising subgenus Spirocarpos, which are morphologically distinct from the remaining species of Medicago, were not clearly distinguishable from the other species collectively on the basis of phenolic chemistry. However, within subgenus Spirocarpos the most sharply distinguished subgroup on morphological criteria, section Pachyspirae, tended to be different chemically from the remaining species of the subgenus. When the species of Medicago except for subgenus Spirocarpos were analysed separately, it was found that the two major phylads of these tended to be distinguishable chemically. These included a group of perennials (subgenus Medicago section Falcago) and a group of peculiar species (subgenus Orbicularia) tending morphologically towards the genus Trigonella). Appreciable intraspecific diversity was found for phenolic chemistry but significantly less than interspecific variation. In a few cases species which are quite similar morphologically diverged chemically, most notably the two species of subgenus Lupularia.
Classification of fens near southern James Bay, Ontario, using vegetational physiognomy
Authors: Sims Richard A. , Cowell Daryl W. , Wickware Greg M.
Published: October 2007

On the basis of vegetational physiognomy, 47 sites within 1 to 43 km of the southern James Bay coast were classified in the field into four fen types: graminoid, low shrub, graminoid-rich treed, and sphagnum-rich treed. The four types are directly related to differences in vegetational cover and in soil and water parameters, specifically depth to water level, peat thickness, selected groundwater nutrients, and distance from the coast. Detrended correspondence analysis was used to ordinate the vegetational cover of the fen sites. No one or two of the 16 soil and water parameters obtained in this study could be used to discriminate conclusively among fen types. Linear discriminant function (LDF) analysis, however, indicated that the better discriminators were pH, peat thickness, SO4−, K+, and depth to water level. When all water and soil parameters were used, regrouping by LDF analysis into the four a priori groups was achieved with 78% accuracy. Canonical analysis also showed separations when soil and water parameters for sites were plotted in two dimensions. Because of isostatic rebound, distance from the coast represents a temporal as well as a spatial gradient. Peat depth in the fens increases with distance from the coast, at a mean rate of 4.7 cm for each kilometre inland. Na+ plus Cl− in the groundwater of the fens decreases asymptotically with increasing distance from the coast.
La première feuille des plantules d'orge. II. Croissance en longueur
Authors: Silvy A.
Published: October 2007

The growth in length, of the first leaf was studied after an improvement by line breeding and seed grading. Similar to leaf initiation which occurs in two distinct periods for the blade and for the sheath, the growth curve of the whole leaf equals the sum of the growth curves for the blade and for the sheath, respectively. The relative growth rate for the whole leaf reaches a maximum, then decreases with a shoulder. The maximum corresponds to the greatest relative growth rate for the blade. The change in the rate of decrease corresponds to the beginning of the sheath growth at the moment when the blade is emerging.
Histogenesis of sugarcane callus originating from young leaf and stem tip explants
Authors: Liu Ming-Chin , Chen Wen-Huei , Shih Soh-Chao
Published: October 2007

The site of callus initiation in sugarcane (Saccharum sp.) rolled young leaf and stem tip explants was histologically traced. It was found that the callus initials in the former were derived from the parenchyma adjacent to the primary phloem, whereas those in the latter arose from the primary phloem itself. The initial callus cells proliferated periclinally and consequently a nodulelike callus mass was formed after 40 days in culture. This finding is discussed in relation to its significance for in vitro mutation induction.
Noncompetitive effects of Kochia scoparia on grain sorghum and soybeans
Authors: Einhellig Frank A. , Schon Mary K.
Published: October 2007

The allelopathic potential of Kochia scoparia (L.) Schrad., a common weed in cultivated fields, was demonstrated on grain sorghum and soybeans. Growth of sorghum seedlings was reduced when the nutrient medium contained an extract equivalent of 1 g fresh weight of Kochia in 60 mL of nutrient solution, or higher quantities. Soybean seedling growth was depressed by as little as 1 g of Kochia in 240 mL of nutrient solution. Treatments with Kochia extracts that reduced growth also caused seedlings to have either an increase in leaf diffusive resistance, a decrease in water potential, or both. The addition of dried Kochia to soil pots in which seedlings were germinated and grown showed that 0.5 g of debris per 80 g of soil resulted in a significant reduction in sorghum growth, and seedlings grown with 2.0-g additions also had an increase in leaf resistance and decrease in water potential. Effects on water metabolism are indicated as one mechanism of action of allelochemicals from Kochia. It is suggested that biochemical interference from Kochia weeds in sorghum and soybean fields can contribute to production losses.
Spore ontogeny in species of Phillipsia and Wynnea (Pezizales)
Authors: Li Li-Tzu , Kimbrough James W.
Published: October 2007

Some species of the genera Phillipsia and Wynnea have similar longitudinally ridged cyanophobic ascospore markings. Ultrastructural studies show that the cyanophobic spore markings are part of the primary wall. In contrast, the cyanophilous spore ornaments are formed by the secondary wall. The observation of spore wall development indicates that the sources of the spore wall components are the sporoplasm and the epiplasm. Based on the pinkish hymenial color of fresh young apothecia and the cyanophobic spore ridges found only in some members of the Sarcoscyphaceae, Wynnea belongs to the Sarcoscyphaceae. Keywords: Pezizales, Phillipsia, Sarcoscyphaceae, spore wall ontogeny, ultrastructure, Wynnea.