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The species composition of a plant community can affect the distribution and abundance of other organisms including plant pathogens. The goal of this study was to understand the role of host diversity in the transmission of two Barley yellow dwarf virus (BYDV) species that share insect vectors and hosts. Greenhouse experiments measured the transmission rate of BYDV species PAV and PAS from infected oat plants to healthy agricultural and wild grasses and from these species back to healthy oat seedlings. In the field component of the study, the rate of spread of PAV and PAS was measured in monoculture plots planted with agricultural grasses. In greenhouse experiments, the aphid vector more readily transmitted PAV from agricultural grasses and more readily inoculated PAS to the wild grass species assayed. In the field experiment, disease prevalence was greater in wheat, but there was no difference in the rate of spread of PAV and PAS. These results indicate an interaction between vector and host genotype that selects for greater PAV transmission in grain crops, contributes to differences in disease prevalence between grass types, and maintains pathogen diversity within the larger plant community (i.e. agricultural and non-agricultural hosts).

This paper considers 4-dimensional manifolds upon which there is a Lorentz metric, h, and a symmetric connection and which are originally assumed unrelated. It then derives sufficient conditions on the metric and connection (expressed through the curvature tensor) for the connection to be the Levi-Civita connection of some (local) Lorentz metric, g, and calculates the relationship between g and h. Some examples are provided which help to assess the strength of the sufficient conditions derived.

Energy dispersive X-ray fluorescence (EDXRF) was used to nondestructively determine the elemental composition of current-size $10 United States Federal Reserve Notes (FRN) from series 1928 to series 2003. The X-ray spectra from all the bank notes were cataloged into a digital spectral library for searching and comparisons of questioned bank notes. Paper and different color printing inks were analyzed to determine elemental composition. One of the components of the green ink on the back of the early issues was identified as being the compound pigment Pigment Green 15, also known as chrome green (PbSO4·xPbCrO4·yFe4[Fe(CN)6]) precipitated onto a base of baryte (BaSO4) and Paris white (CaCO3). Our data show that the concentrations of Pb in the green ink have declined since the first issue of Series 1928 and ended with Series 1988. EDXRF is an excellent analytical method for rapid nondestructive elemental analysis of bank notes. This elemental characterization is useful for authenticating bank notes for the numismatist and for the forensic scientist. The method described can also be used for quality control in the manufacture of bank notes and for evaluating how circulating bank notes deteriorate.

It is shown that the only conformal or projective vector fields admitted by the Reissner-Nordstrom metric are its standard Killing vector fields.

Three-dimensional manifolds admitting Lorentz metrics are studied. The first part of the paper gives a classification of the Ricci and curvature tensors and also of the conformal (Schouten–Cotton–York) tensor. The second part of the paper investigates Killing and conformal symmetry and also the nature of the zeros of the associated vector fields. The maximum dimension of the Killing and conformal algebras is calculated. A theorem regarding the reduction of the conformal algebra to a Killing algebra of a conformally related metric is given.

The motivation for this paper is the recent interest in the study of symme tries in general relativity and its purpose is to discuss the mathematical foundations required for such a study. The general (formal and informal) ideas of what constitutes a symmetry of space-time are discussed and developed and the idea of a Lie algebra of symmetry vector fields is studied in detail. The relationship between such Lie algebras and the ideas of Lie transformation group theory (Palais' theorems) is stated and a general theorem regarding the orbits of such symmetries is given. Finally some specific symmetries in general relativity are explored and some of their similarities and differences noted.

Those space-times admitting special conformal vector fields and those admitting special projective vector fields have recently been studied. In this paper these two classes of space times are shown to be very closely related to each other. Certain uniqueness features of (and necessary extra symmetries contained in) the associated Lie algebras are discussed and the dimensionality of each of the algebras is computed.

Inadequate species definitions present a serious problem to the pathologist working in plant hygiene or quarantine which demands urgent attention. Species concepts in the downy mildews have not kept pace with developments in evolutionary and molecular biology, or with advances in ecological genetics, because the downy mildews are obligate biotrophs that are not easily cultured in the laboratory. Existing approaches to species concepts in this group (morphometric, Ga¨umann’s ‘biological species’ and Skalicý’s ‘eco–physio–phentic’ concepts) are examined and found to be inadequate and potentially misleading. The systematic treatment of the downy mildews is beginning to benefit from the application of modern methods of systematic analysis. The contribution and potential of ultrastructure, karyotyping, sterol and fatty acid composition, isoenzyme patterns, molecular biology, numerical methods, immunoassay and hypotheses of coevolution to the development of species concepts are reviewed and their wider application is seen as a priority. The application to the downy mildews of two widespread species concepts, the biological and phylogenetic concepts, is examined in the light of the information gained from modern methods of analysis, but neither is found adequate to describe species of downy mildews as they occur in nature. Modern methods can suggest phylogenetic relationships on the basis of statistical probabilities and may also detect microevolutionary change, but it is concluded that much more information is required about individual breeding systems, gene flow, ecology, phylogeny and distribution before informed decisions about the delimitation of most species can be made. Until patterns of genetic diversity can be established, a modified phylogenetic species concept may offer one interim solution to the problem of species definition in the downy mildews.

It is shown that a spacetime admitting symmetries may be disjointly decomposed into an open dense finite union of open sets in each of which the type (spacelike, timelike or null) and dimension of the symmetry orbits and the Petrov type of the Weyl tensor are constant, together with a closed non-empty subset of M which has no interior. It is also shown that if the symmetries admitted are affine (including Killing and homothetic), conformal or projective, the subset of points of M at which the orbit dimension is maximum is open and dense (i.e. `almost everywhere') in M.

— The isotopic abundances of Ni in 17 metallic spheroids from Meteor Crater, Arizona, were determined by inductively coupled plasma mass spectrometry (ICP-MS). Sixteen spheroids have normal isotopic abundances. A 17th shows a marginally detectable mass fractionation of 0.40 ± 0.14 %/AMU in favor of the heavier isotopes. The general absence of mass fractionation indicates that open system evaporation caused little loss of Ni. Variable activities of the cosmogenic radionuclides 10Be and 26Al were measured by accelerator mass spectrometry in separate suites of spheroids. Activities of 26Al in most samples and of 10Be in metal cores separated from spheroids indicate that they either (1) come from greater depths in the parent meteoroid than do hand specimens, or (2) lost Al and Be during the process of spheroid formation. One individual spheroid has 10Be and 26Al activities comparable to those of bulk specimens. This result suggests that spheroid formation may occasionally include material from the outermost meter or so of the impactor. Relatively high activities of 10Be, ∼3 dpm/kg, in the siliceous shells of Canyon Diablo spheroids very likely have a meteoric origin.

A general discussion of affine vector fields (collineations) in space–time is given following a previous article by Hall and da Costa. Some general remarks are presented on the zeros of affine vector fields and then the general theory of such zeros is established. Some preliminary results regarding homothetic symmetries in two‐ and three‐dimensional space–times are also given. The impossibility of reducing an affine algebra containing proper affine vector fields to homothetic or Killing vector fields, by means of a change of compatible metric, is demonstrated.

A study is made of Weyl connections and their associated holonomy groups. The extent to which a Weyl connection determines its associated metric and 1‐form structures is also discussed. Finally, the related concept of a locally metric connection is introduced and some relations between metric, locally metric, and Weyl connections are established.

This paper is concerned with the sectional curvature function on space‐time and discusses vector fields that generate symmetries of this function. It is shown that such vector fields form a Lie algebra and its general structure and the possibilities for its dimension are given. A consequence of the paper is a complete discussion of the Lie algebra of conformal vector fields for conformally flat plane waves.

From a group of 96 specimens ranging in thickness from 15 to 38 mm (0.60 to 1.50 in.), a regression equation was obtained for Ti.6A1-4V plate relating the fracture toughness, K Q , of 205-mm (8-in.) wide specimens to the variables of specimen thickness and fracture toughness, K Q , for 76-mm (3-in.) width. The fracture toughness value of Ti-6Al-4V plate can be increased appreciably in thin specimens by using an oversized width specimen. The magnitude of this toughness increase diminishes as the thickness increases and approaches 38-mm (1.5-in.). Oversizing the specimen results in a significant reduction in the stress at instability at 2 percent crack extension. The specimen strength ratio, R s c , essentially remains the same while K m a x and the P m a x /P Q ratio increase. Crack-growth-resistance curves constructed from load versus crack-opening-displacement curves for the two different width specimens are similar. This indicates the fracture behavior is the same and not altered with increased specimen width. Furthermore, K values for oversized specimens can be calculated from the loads at the appropriate crack extension in smaller standard size specimens, and vice versa.

On the basis of phenotypic characterization and DNA relatedness determinations, the genus Afipia gen. nov., which contains six species, is described. The type species is Afipia felis sp. nov. (the cat scratch disease bacillus). Afipia clevelandensis sp. nov., Afipia broomeae sp. nov., and three unnamed not associated with cat-borne disease. All but one strain (Afipia genospecies 3) were isolated from human wound and respiratory sources. All Afipia species are gram-negative, oxidase-positive, nonfermentative rods in the alpha-2 subgroup of the class Proteobacteria. They are motile by means of a single flagellum. They grow on buffered charcoal-yeast extract agar and nutrient broth, but rarely on MacConkey agar, at 25 and 30 degrees C. They are urease positive; but they are negative in reactions for hemolysis, indole production, H2S production (triple sugar iron agar), gelatin hydrolysis, esculin hydrolysis, and peptonization of litmus milk. They do not produce acid oxidatively from D-glucose, lactose, maltose, or sucrose. The major cell wall fatty acids are 11-methyloctadec-12-enoic (CBr19:1), cis-octadec-11-enoic (C18:1omega7c), and generally, 9,10-methylenehexadecanote and 11,12-methyleneoctadecanoate; and there are only trace amounts of hydroxy acids. The guanineplus-cytosine content is 61.5 to 69 mol%. A. felis is positive for nitrate reduction and is delayed positive for acid production from D-xylose, but it is catalase negative. A. clevelandensis is negative in all of these tests. A. broomeae is weakly positive for catalase production and acid production from D-xylose, but it is negative for nitrate reduction.

This paper is the second of a set of two papers on curvature collineations in general relativity. The first paper presented the mathematical basis of curvature collineations and a possible approach to their study. This paper continues from the first one by investigating in detail many of the cases where curvature collineations can occur in space‐time. It is based on a classification of the curvature tensor which is discussed in the first paper and reviewed briefly here. This, together with the geometrical approach favored in this paper, leads to a rather general discussion of the problem which, it is hoped, does not obscure those physical aspects of the situation that are important in Einstein’s theory.

A multicenter study was performed to evaluate the effect of medium, incubation time (24 and 48 h), and temperature (30 and 35 degrees C) on intra- and interlaboratory variations in MICs of flucytosine, amphotericin B, and ketoconazole for yeasts. Testing was performed on coded isolates of Candida species (11 strains) and Cryptococcus neoformans (2 strains) by using a standard macrodilution protocol 11 laboratories. Four chemically defined media buffered to pH 7.0 with morpholinepropanesulfonic acid were evaluated, including buffered yeast nitrogen base, synthetic amino acid medium-fungal, RPMI 1640 medium, and high-resolution antifungal assay medium. Intralaboratory variability was less than or equal to fourfold for 97% of the replicate sets of data. The highest level of interlaboratory agreement, irrespective of antifungal agent or incubation conditions, was observed with RPMI 1640 medium. Intralaboratory variability was less than or equal to fourfold for 93% of the determinations with ketoconazole and 100% with flucytosine tested in RPMI 1640 medium at 35 degrees C for 24 h. Variability in amphotericin B results was less than or equal to fourfold for 81% of the determinations in RPMI 1640 medium at 35 degrees C for 48 h. The rank order of MICs within each antifungal test group was similar among the various laboratories and was generally in agreement with the reference rank order regardless of the test medium that we used.

A general study is made of conformal vector fields on a four‐dimensional Lorentz manifold with particular emphasis being laid on the structure of the zeros (critical points) of such vectors fields. The implications for general relativity are investigated and a discussion of conformal vector fields in generalized plane wave space‐times is given. An attempt is made to clarify the well‐known theorem of Bilyalov and Defrise‐Carter.

A multilaboratory collaborative study was undertaken to determine whether the anaerobic disk diffusion test of Horn et al. could be performed reproducibly and accurately. Tests with nine different antimicrobial disks were evaluated. Reproducibility of the agar diffusion disk method was similar to that of the reference agar dilution test procedure. The anaerobic disk diffusion procedure was found to be a potentially useful method for testing some antimicrobial agents against rapidly growing anaerobes belonging to the Bacteroides fragilis group. These promising results warrant further investigations and validations.

Dematiaceous fungi are a cause of a variety of human infections, including phaeohyphomycosis, that may affect patients with solid organ or bone marrow transplants. Exophiala jeanselmei, the most common cause of the pheomycotic cyst/subcutaneous phaeohyphomycosis in the United States, has been shown to cause disease in transplant recipients. We report a lung-transplant patient with relapsing and invasive E. jeanselmei phaeohyphomycosis, who previously had a pheomycotic cyst excised and treated with oral fluconazole. The patient was subsequently treated with re-excision and an 8-month course of oral itraconazole without relapse as to date.

Some recent results of Beem and Parker regarding tidal accelerations and the algebraic structure of the Riemann tensor are generalized.

Invasive zygomycosis is rapidly progressive and is associated with angioinvasion and infarction. Invasive disease requires emergent surgical and medical intervention. Because it is important for surgical pathologists to recognize these fungi and their preferential sites of growth, the objective of this article is to describe the fungal morphology and histopathologic findings in biopsies from patients with zygomycotic disease, with emphasis on preferential sites of fungal growth.Medical record and histologic review identified 20 patients with zygomycosis. Inclusion criteria included the presence of typical ribbonlike hyphae and positive culture, a clinical history of invasive zygomycosis, or both. The histologic features of disease and the fungal morphology were assessed.Fungus ball (15%), rhinocerebral (55%), and pulmonary (30%) disease were the types of disease represented. The inflammatory responses were predominantly neutrophilic (50%), predominantly granulomatous (5%), pyogranulomatous (25%), or absent (20%). Invasive disease was characterized by prominent infarcts (94%), angioinvasion (100%), and, surprisingly, prominent perineural invasion (90%) in biopsies that contained nerves for evaluation. At least rare hyphal septa were always seen (100%), and most branches (95%) varied from 45 degrees to 90 degrees.As known to mycologists, zygomycetes are pauciseptate, rather than aseptate, molds. Therefore, the presence of an occasional septum is expected. Perineural invasion is a common finding in invasive zygomycosis, as are angioinvasion and infarcts. Therefore, prior to excluding the presence of these fungi in biopsies suspected to contain zygomycetes, the perineural space should be carefully examined.

To assess the clinical significance associated with the identification of fungal elements consistent with Aspergillus in cytology specimens.For all cytology specimens with reported fungal elements consistent with Aspergillus, reported over a 9 yr and 8 mo period at The Cleveland Clinic Foundation, the patient's medical charts were reviewed with particular attention to underlying disease, presentation, treatment, and clinical course. Cytology results were compared with available microbiologic cultures and tissue specimens in all of the patients.Forty-five cytology specimens with Aspergillus fungal forms, from 36 patients, were identified. Twenty-six patients had concurrent specimens sent for culture in whom II grew Aspergillus species (10 Aspergillus fumigatus), eight grew organisms other than Aspergillus, and seven were no growth. A total of 16 patients (44%) were treated with antifungal treatment (Amphotericin B). Treatment with Amphotericin B was significantly associated with a concurrent growth of Aspergillus species (9/11 patients with Aspergillus culture positive vs. 7/25 patients without a positive culture for Aspergillus, P value = 0.004 (ODDS ratio = 11, 95% confidence interval:#1.6-104, 2-tailed Fisher exact test.)The presence of fungal forms consistent with Aspergillus in cytology specimens is neither specific nor sensitive for significant infection due to Aspergillus. Treatment with Amphotericin B is more likely to be instituted when a concurrent clinical specimen grows Aspergillus species in culture.

Using the mitochondrial DNA miniprep technique, the identity of sixteen morphologically unusual cultures allocated to Phytophthora nicotianae, Phytophthora mexicana or Phytophthora porri was determined by comparison with a library of mtDNA band patterns obtained from reference cultures. Seven cultures were identified as Phytophthora nicotianae (including those assigned to Phytophthora mexicana and Phytophthora porri), six as strains of Phytophthora palmivora with small, ovoid, weakly caducous sporangia, and one as Phytophthora citrophthora. Some cultures of P. nicotianae had a low percentage of caducous sporangia. Percentage sporangium caducity, but not sporangium L:B ratio, is considered a useful taxonomic criterion for separating species morphologically similar to Phytophthora nicotianae. One culture from tobacco in New Zealand had a highly unusual morphology and a unique DNA band pattern, but was not identifiable. One culture from Acacia mearnsii in South Africa had a unique DNA band pattern which was identical to that of an isolate from Annona squamosa from Australia previously identified as Phytophthora palmivora, the precise identity of which is still unclear. The identity of most isolates from diseased durian was found to be Phytophthora palmivora, confirming its role as the main pathogen, but P. nicotianae was also identified from this host.

Processing of specimens for mycobacteria need to proceed as rapidly as possible to provide 24 hour turnaround for smears and 21-day turnaround for the identification of Mycobacterium tuberculosis. If these goals are to be accomplished, a broth culture or microcolony plate method must be part of the media and in the planting process. Use of conventional solid media alone does not provide adequate turnaround time.

Molecular-based techniques, such as use of genetic probes, can greatly reduce turnaround time of the identification of some isolates in the clinical microbiology laboratory. For example, culture confirmation of an acid-fast bacillus such as Mycobacterium tuberculosis or Mycobacterium avium-intracellulare by a gene probe can be performed within hours of the isolation of the organism. Conventional methods might require more than 2 to 4 weeks for this identification. Identification of a mold, such as Histoplasma capsulatum, with a gene probe, can be done in less than 24 hours, with minimal growth available; conventional fungal identification takes 1 to 2 weeks or more. Whether a probe is used in the clinical microbiology laboratory depends on a number of factors including accuracy of the probe, cost, commercial availability, and ease of performance. In addition, the relevance of a more rapid result needs to be considered. A gene probe may be more specific than conventional methodologies, and this may increase its advantage. Direct specimen testing with probes is presently hampered by inadequate sensitivities. Prior amplification may decrease this limitation. It is hoped that methods will be available in the near future that provide amplification and probing of clinical specimens for laboratory diagnosis to be made within a short time following specimen collection.

This paper identifies the institutional character of pre-1920 psychology at Clark University with founding President G. Stanley Hall's active "patronage" of "outsiders," argues that the origins of this institutional character can be found in Hall's own personal character and temperament, and traces the influence of this institutional character through much of the psychology done at Clark before 1920.

Consider the curvature tensor components Rbcda on a space-time M calculated from given space-time metric components gab. The number of alternative space-time metrics for M which yield the same curvature components is known to be heavily restricted, the exact ambiguity in the metric being dependent on the form of the curvature components. In this paper it is shown that, in spite of these ambiguities, the algebraic structure of the energy-momentum tensor and the Weyl tensor on M are essentially determined.

In this letter some recent results due to Collins and Lang (ibid. vol. 3, p.1143, (1986)) on homotheties and singularities in Einstein's theory are discussed and extended.

A connection is shown between the Riemannian Curvatures of the wave surfaces of a null vector I at a point p in space-time and the Petrov type of the space-time at p. Some other results on Riemannian Curvature are discussed

SummaryApplication of a skin lotion to the body after showering greatly reduced the number of bacteria and skin scales dispersed from 10 men and 10 women. This effect lasted for at least 4 h when surgical clothing was worn. The use of a skin lotion to reduce bacterial dispersal could provide a simple and inexpensive alternative to an ultraclean air system or uncomfortable operating clothing during surgery requiring these procedures.