Comparison of measured electron energy spectra for six matched, radiotherapy accelerators.

This study compares energy spectra of the multiple electron beams of individual radiotherapy machines, as well as the sets of spectra across multiple matched machines. Also, energy spectrum metrics are compared with central-axis percent depth-dose (PDD) metrics. METHODS: A lightweight, permanent magnet spectrometer was used to measure energy spectra for seven electron beams (7-20 MeV) on six matched Elekta Infinity accelerators with the MLCi2 treatment head. PDD measurements in the distal falloff region provided R50 and R80-20 metrics in Plastic Water® , which correlated with energy spectrum metrics, peak mean energy (PME) and full-width at half maximum (FWHM). RESULTS: Visual inspection of energy spectra and their metrics showed whether beams on single machines were properly tuned, i.e., FWHM is expected to increase and peak height decrease monotonically with increased PME. Also, PME spacings are expected to be approximately equal for 7-13 MeV beams (0.5-cm R90 spacing) and for 13-16 MeV beams (1.0-cm R90 spacing). Most machines failed these expectations, presumably due to tolerances for initial beam matching (0.05 cm in R90 ; 0.10 cm in R80-20 ) and ongoing quality assurance (0.2 cm in R50 ). Also, comparison of energy spectra or metrics for a single beam energy (six machines) showed outlying spectra. These variations in energy spectra provided ample data spread for correlating PME and FWHM with PDD metrics. Least-squares fits showed that R50 and R80-20 varied linearly and supralinearly with PME, respectively; however, both suggested a secondary dependence on FWHM. Hence, PME and FWHM could serve as surrogates for R50 and R80-20 for beam tuning by the accelerator engineer, possibly being more sensitive (e.g., 0.1 cm in R80-20 corresponded to 2.0 MeV in FWHM). CONCLUSIONS: Results of this study suggest a lightweight, permanent magnet spectrometer could be a useful beam-tuning instrument for the accelerator engineer to (a) match electron beams prior to beam commissioning, (b) tune electron beams for the duration of their clinical use, and (c) provide estimates of PDD metrics following machine maintenance. However, a real-time version of the spectrometer is needed to be practical.

Structural character evolution in Pucciniomycotina: mitosis, septa, and hyphal branch initiation in two Helicogloea species.

Early diverging taxa of Ascomycota and Basidiomycota share similarities in subcellular characters of the spindle pole body (SPB), nuclear division, and septal pore apparatus, but our understanding of character evolution is incomplete because of the limited number of structural studies within the earliest diverging subphyla of Dikarya, Taphrinomycotina and Pucciniomycotina. Two species of Helicogloea (Atractiellomycetes) were analyzed for these characters and provide data on SPB and nuclear division for an additional class of Pucciniomycotina. A detailed analysis of septal pore apparatus for the Helicogloea species permits comparisons with those of other Pucciniomycotina and Ascomycota. The endogenous origin of hyphal branches is shown to occur in a third class of Pucciniomycotina. The full set of characters supports a close relationship between Atractiellomycetes and Pucciniomycetes.

Cultural and cytological characterization of Dacryopinax primogenitus, a new species in the Dacrymycetes with a fully sequenced genome.

A Dacryopinax species that was cultured in Costa Rica and fruited in the laboratory provided DNA for the first sequenced genome for the Dacrymycetes. Here we characterize the isolate morphologically and cytologically and name it D. primogenitus Molecular sequences from the nuclear large subunit gene and internal transcribed spacer indicated that it is closely related to the South American D. indacocheae with which it agrees structurally. Both species form conidia on the basidiocarp, and D primogenitus also forms them on the mycelium. Unlike previous reports for the Dacrymycetales postmeiotic nuclear division results in uninucleate basidiospores and six residual nuclei in the basidium after basidiospore discharge. Ultrastructural analysis shows the characteristic septal-pore apparatus for the class and endogenous origin of the epibasidia/sterigmata, which may be a common occurrence in Dacrymycetes and the early diverging orders of its sister class, the Agaricomycetes.

Evolution of zygomycetous spindle pole bodies: Evidence from Coemansia reversa mitosis.

PREMISE OF THE STUDY: The earliest eukaryotes were likely flagellates with a centriole that nucleates the centrosome, the microtubule-organizing center (MTOC) for nuclear division. The MTOC in higher fungi, which lack flagella, is the spindle pole body (SPB). Can we detect stages in centrosome evolution leading to the diversity of SPB forms observed in terrestrial fungi? Zygomycetous fungi, which consist of saprobes, symbionts, and parasites of animals and plants, are critical in answering the question, but nuclear division has been studied in only two of six clades. METHODS: Ultrastructure of mitosis was studied in Coemansia reversa (Kickxellomycotina) germlings using cryofixation or chemical fixation. Character evolution was assessed by parsimony analysis, using a phylogenetic tree assembled from multigene analyses. KEY RESULTS: At interphase the SPB consisted of two components: a cytoplasmic, electron-dense sphere containing a cylindrical structure with microtubules oriented nearly perpendicular to the nucleus and an intranuclear component appressed to the nuclear envelope. Markham's rotation was used to reinforce the image of the cylindrical structure and determine the probable number of microtubules as nine. The SPB duplicated early in mitosis and separated on the intact nuclear envelope. Nuclear division appears to be intranuclear with spindle and kinetochore microtubules interspersed with condensed chromatin. CONCLUSIONS: This is the sixth type of zygomycetous SPB, and the third type that suggests a modified centriolar component. Coemansia reversa retains SPB character states from an ancestral centriole intermediate between those of fungi with motile cells and other zygomycetous fungi and Dikarya.

Functional and phylogenetic implications of septal pore ultrastructure in the ascoma of Neolecta vitellina.

Neolecta represents the earliest derived extant ascomycete lineage (Taphrinomycotina) to produce ascomata. For this reason the genus has been of interest with regard to ascoma evolution in ascomycetes. However, the evidence is equivocal regarding whether the Neolecta ascoma is homologous or analogous to ascomata produced in the later derived ascomycete lineages (Pezizomycotina). We investigated phylogenetically informative septal pore ultrastructure of Neolecta vitellina to compare with Pezizomycotina. We found that crystalline bodies that block nonascogenous septal pores in Neolecta differ from Woronin bodies, a synapomorphy for the Pezizomycotina, in three ways: (i) vacuolar origin, (ii) associated material and (iii) being loosely membrane bound. We also observed a unique type of membranous material within the septal pore, as well as distant from the septal pore, that appears to be associated with the endoplasmic reticulum. The vacuolar crystals and membranous material might have a function analagous to septal pore structures (e.g. Woronin bodies, lamellate structures) in the Pezizomycotina. Morphological evidence from our study supports an independently derived septal pore-occluding structure in the Neolecta lineage.

Cellular organization in germ tube tips of Gigaspora and its phylogenetic implications.

Comparative morphology of the fine structure of fungal hyphal tips often is phylogenetically informative. In particular, morphology of the Spitzenkörper varies among higher taxa. To date no one has thoroughly characterized the hyphal tips of members of the phylum Glomeromycota to compare them with other fungi. This is partly due to difficulty growing and manipulating living hyphae of these obligate symbionts. We observed growing germ tubes of Gigaspora gigantea, G. margarita and G. rosea with a combination of light microscopy (LM) and transmission electron microscopy (TEM). For TEM, we used both traditional chemical fixation and cryo-fixation methods. Germ tubes of all species were extremely sensitive to manipulation. Healthy germ tubes often showed rapid bidirectional cytoplasmic streaming, whereas germ tubes that had been disturbed showed reduced or no cytoplasmic movement. Actively growing germ tubes contain a cluster of 10-20 spherical bodies approximately 3-8 µm behind the apex. The bodies, which we hypothesize are lipid bodies, move rapidly in healthy germ tubes. These bodies disappear immediately after any cellular perturbation. Cells prepared with cryo-techniques had superior preservation compared to those that had been processed with traditional chemical protocols. For example, cryo-prepared samples displayed two cell-wall layers, at least three vesicle types near the tip and three distinct cytoplasmic zones were noted. We did not detect a Spitzenkörper with either LM or TEM techniques and the tip organization of Gigaspora germ tubes appeared to be similar to hyphae in zygomycetous fungi. This observation was supported by a phylogenetic analysis of microscopic characters of hyphal tips from members of five fungal phyla. Our work emphasizes the sensitive nature of cellular organization, and the need for as little manipulation as possible to observe germ tube structure accurately.

The genome of the xerotolerant mold Wallemia sebi reveals adaptations to osmotic stress and suggests cryptic sexual reproduction.

Wallemia (Wallemiales, Wallemiomycetes) is a genus of xerophilic Fungi of uncertain phylogenetic position within Basidiomycota. Most commonly found as food contaminants, species of Wallemia have also been isolated from hypersaline environments. The ability to tolerate environments with reduced water activity is rare in Basidiomycota. We sequenced the genome of W. sebi in order to understand its adaptations for surviving in osmotically challenging environments, and we performed phylogenomic and ultrastructural analyses to address its systematic placement and reproductive biology. W. sebi has a compact genome (9.8 Mb), with few repeats and the largest fraction of genes with functional domains compared with other Basidiomycota. We applied several approaches to searching for osmotic stress-related proteins. In silico analyses identified 93 putative osmotic stress proteins; homology searches showed the HOG (High Osmolarity Glycerol) pathway to be mostly conserved. Despite the seemingly reduced genome, several gene family expansions and a high number of transporters (549) were found that also provide clues to the ability of W. sebi to colonize harsh environments. Phylogenetic analyses of a 71-protein dataset support the position of Wallemia as the earliest diverging lineage of Agaricomycotina, which is confirmed by septal pore ultrastructure that shows the septal pore apparatus as a variant of the Tremella-type. Mating type gene homologs were identified although we found no evidence of meiosis during conidiogenesis, suggesting there may be aspects of the life cycle of W. sebi that remain cryptic.

Orbilia ultrastructure, character evolution and phylogeny of Pezizomycotina.

Molecular phylogenetic analyses indicate that the monophyletic classes Orbiliomycetes and Pezizomycetes are among the earliest diverging branches of Pezizomycotina, the largest subphylum of the Ascomycota. Although Orbiliomycetes is resolved as the most basal lineage in some analyses, molecular support for the node resolving the relationships between the two classes is low and topologies are unstable. We provide ultrastructural evidence to inform the placement of Orbiliomycetes by studying an Orbilia, a member of the only order (Orbiliales) of the class. The truncate ascus apex in the Orbilia is thin-walled except at the margin, and an irregular wall rupture of the apex permits ascospore discharge. Ascus, ascogenous and non-ascogenous hyphae were simple septate, with septal pores plugged by unelaborated electron-dense, non-membranous occlusions. Globose Woronin bodies were located on both sides of the septum. Nuclear division was characterized by the retention of an intact nuclear envelope, and a two-layered disk-shaped spindle pole body. The less differentiated nature of the spore discharge apparatus and septal pore organization supports an earliest diverging position of Orbiliomycetes within the subphylum, while the closed nuclear division and disk-shaped spindle pole body are interpreted as ancestral state characters for Ascomycota.

An ontology of fungal subcellular traits.

UNLABELLED: • PREMISE OF THE STUDY: The Fungal Subcellular Ontology used in the Assembling the Fungal Tree of Life project is a taxon-wide ontology (controlled vocabulary for attributes) designed to clarify and integrate the broad range of subcellular characters and character states used in higher-level fungal systematics. As in the algae, cellular characters are important phylogenetic markers in kingdom Fungi. The Fungal Subcellular Ontology has been developed primarily to help researchers, especially systematists, in their search for information on subcellular characters across the Fungi, and it complements existing biological ontologies, including the Gene Ontology. • METHODS: The character and character state data set used in the Assembling the Fungal Tree of Life Structural and Biochemical Database (http://aftol.umn.edu) is the source of terms for generating the ontology. After the terms were accessioned and defined, they were combined in OBO-Edit file format, and the ontology was edited using OBO-Edit, an open source Java tool supported by the Gene Ontology project. • KEY RESULTS: The Fungal Subcellular Ontology covers both model and nonmodel fungi in great detail and is downloadable in OBO-Edit format at website http://aftol.umn.edu/ontology/fungal_subcellular.obo. • CONCLUSIONS: The ontology provides a controlled vocabulary of fungal subcellular terms and functions as an operating framework for the Assembling the Fungal Tree of Life Structural and Biochemical Database. An ontology-based design enhances reuse of data deposited in the Structural and Biochemical Database from other independent biological and genetic databases. Data integration approaches that advance access to data from the diversity of biological databases are imperative as interdisciplinary research gains importance. In this sense, the Fungal Subcellular Ontology becomes highly relevant to mycologists as well as nonmycologists because fungi interact actively as symbionts and parasites or passively with many other life forms.

Molecular phylogenetics of porcini mushrooms (Boletus section Boletus).

Porcini (Boletus section Boletus: Boletaceae: Boletineae: Boletales) are a conspicuous group of wild, edible mushrooms characterized by fleshy fruiting bodies with a poroid hymenophore that is "stuffed" with white hyphae when young. Their reported distribution is with ectomycorrhizal plants throughout the Northern Hemisphere. Little progress has been made on the systematics of this group using modern molecular phylogenetic tools because sampling has been limited primarily to European species and the genes employed were insufficient to resolve the phylogeny. We examined the evolutionary history of porcini by using a global geographic sampling of most known species, new discoveries from little explored areas, and multiple genes. We used 78 sequences from the fast-evolving nuclear internal transcribed spacers and are able to recognize 18 reciprocally monophyletic species. To address whether or not porcini form a monophyletic group, we compiled a broadly sampled dataset of 41 taxa, including other members of the Boletineae, and used separate and combined phylogenetic analysis of sequences from the nuclear large subunit ribosomal DNA, the largest subunit of RNA polymerase II, and the mitochondrial ATPase subunit six gene. Contrary to previous studies, our separate and combined phylogenetic analyses support the monophyly of porcini. We also report the discovery of two taxa that expand the known distribution of porcini to Australia and Thailand and have ancient phylogenetic connections to the rest of the group. A relaxed molecular clock analysis with these new taxa dates the origin of porcini to between 42 and 54 million years ago, coinciding with the initial diversification of angiosperms, during the Eocene epoch when the climate was warm and humid. These results reveal an unexpected diversity, distribution, and ancient origin of a group of commercially valuable mushrooms that may provide an economic incentive for conservation and support the hypothesis of a tropical origin of the ectomycorrhizal symbiosis.

Reclassification of Pterulaceae Corner (Basidiomycota: Agaricales) introducing the ant-associated genus Myrmecopterula gen. nov., Phaeopterula Henn. and the corticioid Radulomycetaceae fam. nov.

Pterulaceae was formally proposed to group six coralloid and dimitic genera: Actiniceps (=Dimorphocystis), Allantula, Deflexula, Parapterulicium, Pterula, and Pterulicium. Recent molecular studies have shown that some of the characters currently used in Pterulaceae do not distinguish the genera. Actiniceps and Parapterulicium have been removed, and a few other resupinate genera were added to the family. However, none of these studies intended to investigate the relationship between Pterulaceae genera. In this study, we generated 278 sequences from both newly collected and fungarium samples. Phylogenetic analyses supported with morphological data allowed a reclassification of Pterulaceae where we propose the introduction of Myrmecopterula gen. nov. and Radulomycetaceae fam. nov., the reintroduction of Phaeopterula, the synonymisation of Deflexula in Pterulicium, and 53 new combinations. Pterula is rendered polyphyletic requiring a reclassification; thus, it is split into Pterula, Myrmecopterula gen. nov., Pterulicium and Phaeopterula. Deflexula is recovered as paraphyletic alongside several Pterula species and Pterulicium, and is sunk into the latter genus. Phaeopterula is reintroduced to accommodate species with darker basidiomes. The neotropical Myrmecopterula gen. nov. forms a distinct clade adjacent to Pterula, and most members of this clade are associated with active or inactive attine ant nests. The resupinate genera Coronicium and Merulicium are recovered in a strongly supported clade close to Pterulicium. The other resupinate genera previously included in Pterulaceae, and which form basidiomes lacking cystidia and with monomitic hyphal structure (Radulomyces, Radulotubus and Aphanobasidium), are reclassified into Radulomycetaceae fam. nov. Allantula is still an enigmatic piece in this puzzle known only from the type specimen that requires molecular investigation. A key for the genera of Pterulaceae and Radulomycetaceae fam. nov. is also provided here.

Multiple isolations of a culturable, motile Ichthyosporean (Mesomycetozoa, Opisthokonta), Creolimax fragrantissima n. gen., n. sp., from marine invertebrate digestive tracts.

A fragrant, spherical, osmotrophic eukaryote was isolated 27 times from the digestive tracts of marine invertebrates collected from the Northeast Pacific. The isolates were cultured from 7 animal collections over a 2-year period, most from the peanut worm, Phascolosoma agassizii. A small subunit ribosomal DNA phylogeny placed the spherical organism within the ichthyosporea, closest to Sphaeroforma arctica and Pseudoperkinsus tapetis. Supporting the close relationship of isolates, the sequences of ribosomal gene internal transcribed spacers determined for 26 isolates were identical, as were the elongation factor 1-alpha-like gene fragments from 7 isolates. Dispersal via amoeboid cells distinguished this species from its closest relatives and led to the erection of a new genus and species, "Creolimax fragrantissima." Vegetative cells reproduced asexually in vitro after they reached 30-60 microm in diameter by producing amoebae or endospores, which escaped through openings in the parent cell wall. Ultrathin sections of vegetative cells prepared by high-pressure-freeze substitution provided some of the first images of ichthyosporean spindle pole bodies and document, for the first time, tubular extensions of the plasma membrane into an electron-translucent inner layer of the cell wall. Ichthyosporeans are parasites and commensals of animals and culturable species are few. Because "C. fragrantissima" can be isolated regularly and repeatedly from nature and then grown easily through cycles of asexual reproduction, it has the potential to serve as a model organism for further research into marine ichthyosporeans.

Conservation of cytoplasmic organization in the cystidia of Suillus species.

Cystidia of Suillus americanus and S. granulatus (Boletales) were examined cytochemically and ultrastructurally with cells prepared by freeze substitution. We present the first study showing ultrastructural details and cytological functions of the cystidium to be conserved in two closely related species. The results are presented for inclusion in the AFTOL Structural and Biochemical Database to aid in the application of morphological characters to phylogenetic studies. The cystidia of these Suillus species appear to be united by a series of conserved characters, including specialized secretion mechanisms, smooth tubular endoplasmic reticulum and abundant free ribosomes. The conservation of these subcellular traits among members of this genus suggests that ultrastructural details of cystidia may provide a suite of phylogenetically informative characters. Inclusion of such characters in phylogenetic analyses might resolve or provide support for monophyletic groups at the level of family or genus.

Image Quality and Segmentation.

Algorithms for image segmentation (including object recognition and delineation) are influenced by the quality of object appearance in the image and overall image quality. However, the issue of how to perform segmentation evaluation as a function of these quality factors has not been addressed in the literature. In this paper, we present a solution to this problem. We devised a set of key quality criteria that influence segmentation (global and regional): posture deviations, image noise, beam hardening artifacts (streak artifacts), shape distortion, presence of pathology, object intensity deviation, and object contrast. A trained reader assigned a grade to each object for each criterion in each study. We developed algorithms based on logical predicates for determining a 1 to 10 numeric quality score for each object and each image from reader-assigned quality grades. We analyzed these object and image quality scores (OQS and IQS, respectively) in our data cohort by gender and age. We performed recognition and delineation of all objects using recent adaptations [8, 9] of our Automatic Anatomy Recognition (AAR) framework [6] and analyzed the accuracy of recognition and delineation of each object. We illustrate our method on 216 head & neck and 211 thoracic cancer computed tomography (CT) studies.

Septal pore apparatus and nuclear division of Auriscalpium vulgare.

Ultrastructure of the septal pore apparatus and nuclear division of Auriscalpium vulgare (Russulales) was examined with freeze substitution and is presented for inclusion in the AFTOL Structural and Biochemical Database (http://aftol.umn.edu). Previously unreported septal characters for the Russulales (Agaricomycotina) were observed: Septa of the hymenophore had bell-shaped perforated septal pore caps that may extend along the septum and a zone of organelle exclusion surrounded the septal pore apparatus. Metaphase I of meiosis and metaphase of mitosis were similar. Globular spindle pole bodies with electron-opaque inclusions were set within polar fenestrae of the nuclear envelope. The nuclear envelope was mostly intact with occasional gaps. Fragments of endoplasmic reticulum were present near the spindle pole bodies but did not form a polar cap. Structural characters may distinguish one or more clades of the Agaricomycotina and provide additional signal in phylogenetic analyses.

A molecular and morphological re-examination of the generic limits of truffles in the tarzetta-geopyxis lineage - Densocarpa, Hydnocystis, and Paurocotylis.

Truffle species within the /tarzetta-geopyxis lineage share smooth, globose, hyaline spores, but differ in the amount of convolution of hymenia in ascomata. The relationships among truffle species in this lineage have historically been confused. Phylogenetic analyses of the ITS and 28S nuclear ribosomal DNA from recently collected members of the /tarzetta-geopyxis lineage from Asia, Austral Asia, North America, and South America prompted a reinvestigation of species and generic limits in the truffle genera Hydnocystis, Paurocotylis, and Stephensia. Our analyses support emendations of Hydnocystis and Paurocotylis, abandonment of Stephensia and the resurrection of the genus Densocarpa. Nomenclatural changes include the transfer of Stephensia bombycina to Hydnocystis, the transfer of Hydnocystis singeri and Stephensia bynumii to Paurocotylis, the reinstatement of Densocarpa for Stephensia shanori and transfer of Stephensia crocea to Densocarpa. This is the first detection of the genus Paurocotylis in the Americas. We describe three new species, Hydnocystis transitoria from North America, Paurocotylis patagonica from South America, and Paurocotylis watlingii from Australia. Our work highlights the unexplored diversity, morphological plasticity, and remaining taxonomic problems among truffles in the /tarzetta-geopyxis lineage.

Reconstructing the Clavariaceae using nuclear large subunit rDNA sequences and a new genus segregated from Clavaria.

Fungi that produce clavarioid fruit bodies have evolved independently many times in the Basidiomycota. The evolutionary significance of this morphology is difficult to interpret because the phylogenetic positions of many clavarioid fungi are still unknown. In this study we examined the phylogenetic diversity of the Clavariaceae sensu lato among Homobasidiomycetidae by adding partial nuclear large subunit ribosomal DNA sequences from clavarioid and corticioid fungi to a large euagaric dataset and analyzing them both together and separately. Our results indicate that the clavarioid morphology has evolved at least five times in the euagarics while the inclusion of type species enabled us to evaluate the taxonomic consequences of this polyphyletic distribution. Although the sampling available at present is incomplete, a qualitative assessment of our phylogenetic hypotheses indicates that the clavarioid habit might not be as evolutionary labile as previously reported. We propose the new genus Alloclavaria to accommodate Clavaria purpurea, which is not related to Clavaria but is derived within the hymenochaetoid clade. The Physalacriaceae and Clavariaceae are redefined to reflect monophyletic groups, and the limits of Clavaria, Clavulinopsis and Ramariopsis should be reconsidered when additional data are available.

An overview of the higher level classification of Pucciniomycotina based on combined analyses of nuclear large and small subunit rDNA sequences.

In this study we provide a phylogenetically based introduction to the classes and orders of Pucciniomycotina (= Urediniomycetes), one of three subphyla of Basidiomycota. More than 8000 species of Pucciniomycotina have been described including putative saprotrophs and parasites of plants, animals and fungi. The overwhelming majority of these (approximately 90%) belong to a single order of obligate plant pathogens, the Pucciniales (= Uredinales), or rust fungi. We have assembled a dataset of previously published and newly generated sequence data from two nuclear rDNA genes (large subunit and small subunit) including exemplars from all known major groups in order to test hypotheses about evolutionary relationships among the Pucciniomycotina. The utility of combining nuc-lsu sequences spanning the entire D1-D3 region with complete nuc-ssu sequences for resolution and support of nodes is discussed. Our study confirms Pucciniomycotina as a monophyletic group of Basidiomycota. In total our results support eight major clades ranked as classes (Agaricostilbomycetes, Atractiellomycetes, Classiculomycetes, Cryptomycocolacomycetes, Cystobasidiomycetes, Microbotryomycetes, Mixiomycetes and Pucciniomycetes) and 18 orders.

Permanent-magnet energy spectrometer for electron beams from radiotherapy accelerators.

PURPOSE: The purpose of this work was to adapt a lightweight, permanent magnet electron energy spectrometer for the measurement of energy spectra of therapeutic electron beams. METHODS: An irradiation geometry and measurement technique were developed for an approximately 0.54-T, permanent dipole magnet spectrometer to produce suitable latent images on computed radiography (CR) phosphor strips. Dual-pinhole electron collimators created a 0.318-cm diameter, approximately parallel beam incident on the spectrometer and an appropriate dose rate at the image plane (CR strip location). X-ray background in the latent image, reduced by a 7.62-cm thick lead block between the pinhole collimators, was removed using a fitting technique. Theoretical energy-dependent detector response functions (DRFs) were used in an iterative technique to transform CR strip net mean dose profiles into energy spectra on central axis at the entrance to the spectrometer. These spectra were transformed to spectra at 95-cm source to collimator distance (SCD) by correcting for the energy dependence of electron scatter. The spectrometer was calibrated by comparing peak mean positions in the net mean dose profiles, initially to peak mean energies determined from the practical range of central-axis percent depth-dose (%DD) curves, and then to peak mean energies that accounted for how the collimation modified the energy spectra (recalibration). The utility of the spectrometer was demonstrated by measuring the energy spectra for the seven electron beams (7-20 MeV) of an Elekta Infinity radiotherapy accelerator. RESULTS: Plots of DRF illustrated their dependence on energy and position in the imaging plane. Approximately 15 iterations solved for the energy spectra at the spectrometer entrance from the measured net mean dose profiles. Transforming those spectra into ones at 95-cm SCD increased the low energy tail of the spectra, while correspondingly decreasing the peaks and shifting them to slightly lower energies. Energy calibration plots of peak mean energy versus peak mean position of the net mean dose profiles for each of the seven electron beams followed the shape predicted by the Lorentz force law for a uniform z-component of the magnetic field, validating its being modeled as uniform (0.542 ± 0.027 T). Measured Elekta energy spectra and their peak mean energies correlated with the 0.5-cm (7-13 MeV) and the 1.0-cm (13-20 MeV) R90 spacings of the %DD curves. The full-width-half-maximum of the energy spectra decreased with decreasing peak mean energy with the exception of the 9-MeV beam, which was anomalously wide. Similarly, R80-20 decreased linearly with peak mean energy with the exception of the 9 MeV beam. Both were attributed to suboptimal tuning of the high power phase shifter for the recycled radiofrequency power reentering the traveling wave accelerator. CONCLUSIONS: The apparatus and analysis techniques of the authors demonstrated that an inexpensive, lightweight, permanent magnet electron energy spectrometer can be used for measuring the electron energy distributions of therapeutic electron beams (6-20 MeV). The primary goal of future work is to develop a real-time spectrometer by incorporating a real-time imager, which has potential applications such as beam matching, ongoing beam tune maintenance, and measuring spectra for input into Monte Carlo beam calculations.

Long-term increase in nitrogen supply alters above- and below-ground ectomycorrhizal communities and increases the dominance of Russula spp. in a temperate oak savanna.

• Here we examine the effects of increased nitrogen (N) supply on the ectomycorrhizal fungal communities of a temperate oak savanna. • In a 16-yr N-addition experiment in which replicate 1000 m2 plots received 0, 5.4 or 17 g N m-2  yr-1 , ectomycorrhizal sporocarp production was measured in the 14th, 15th and 16th year of fertilization. Ectomycorrhizal fungi (EMF) colonizing roots were examined by morphotyping-PCR-RFLP and sequence analysis in the 14th and 15th year of fertilization. • Total sporocarp richness was reduced by > 50% in both fertilization treatments in all 3 yrs, whereas Russula spp. produced approx. five times more sporocarps with 17 g N m-2  yr-1 . Below-ground, treatment-scale species richness and species area curves were lower with 17 g N m-2  yr-1 but richness, diversity indices and evenness at smaller spatial scales were not. Dominant fungi colonizing roots included Cenococcum geophilum, common in all treatments, Cortinarius spp., dominant in unfertilized plots, and Russula spp., dominant with 17 g N m-2  yr-1 . • Communities of EMF in this temperate deciduous ecosystem responded to N addition similarly to those of coniferous ecosystems in that increased N supply altered EMF diversity and community composition but differently in that dominance of Russula spp. increased.