bluuebunny/crossref_metadata_2025 huggingface dataset:
Ground Truth and Virtual Reality: Hacking vs. Van Fraassen
Authors: Seager William
Published: December 2007

Hacking argues against van Fraassen's constructive empiricism by appeal to features of microscopic imaging. Hacking relies on both our practices involving imaging instruments and the structure of the images produced by these micropractices. Van Fraassen's reply is formally correct yet fundamentally unsatisfying. I aim to strengthen van Fraassen's reply, but must then extend constructive empiricism, specifically the central notion of “theoretical immersion.” I argue that immersion is more analogous to entering a virtual reality than to learning a language. This metaphor assimilates instrument-based practice as well as theoretical debate and explanation, and can provide an anti-realist view of our micro-practices consonant with constructive empiricism.
Is Newtonian Cosmology Really Inconsistent?
Authors: Malament David B.
Published: December 2007

John Norton has recently argued that Newtonian gravitation theory (at least as applied to cosmological contexts where one envisions the possibility of a homogeneous mass distribution throughout all of space) is inconsistent. I am not convinced. Traditional formulations of the theory may seem to break down in cases of the sort Norton considers. But the difficulties they face are only apparent. They are artifacts of the formulations themselves, and disappear if one passes to the so-called “geometrized” formulation of the theory.
Central Place Theory and the Reciprocity Between Theory and Evidence
Authors: Kosso Peter , Kosso Cynthia
Published: December 2007

Information about the prehistoric past is available only in the material remains. To be meaningful, these remains must be interpreted under the influence of a theory of some general or specific aspect of the past. For this reason, prehistoric archaeology clearly shows the reciprocity between theory and evidence and the tension between having to impose information on the evidence in order to discover information in the evidence. We use a specific case in the archaeology of Minoan Crete, a case that uses Central Place Theory as a guide to understanding the evidence, to demonstrate a coherence model of scientific knowledge.
Relativistic Quantum Mechanics and the Conventionality of Simultaneity
Authors: Gunn David , Vetharaniam Indrakumar
Published: December 2007

1. Introduction Dirac's (Dirac 1928) theory of the electron was the first widely accepted relativistic quantum theory, and it later provided the basis for constructing the modern electromagnetic theory of quantum electrodynamics (QED). Whereas Dirac's theory in its simplest form describes relativistic freely-propagating massive non-chiral particles of spin-½, QED describes how such particles interact with one another electromagnetically, via a dynamical quantum field.
Content, Causal Powers, and Context
Authors: Butler Keith
Published: December 2007

Owens (1993) argues that one cannot accept the anti-individualistic conclusions of arguments inspired by Twin Earth thought experiments and still maintain that folk psychological states causally explain behavior. Saidel (1994) has argued that Owens' argument illegitimately individuates the contents of folk psychological states widely and causal powers narrowly. He suggests that causal powers may well be wide, and that the conditions that militate in favor of wide content also militate in favor of wide causal powers; mutatis mutandis for narrow content and narrow causal powers. I argue that these suggestions are in error, and hence that Saidel's criticism is ineffective. Owens' original point is therefore likely to stand.
The Rhetoric of Antirealism and the Copenhagen Spirit
Authors: Beller Mara
Published: December 2007

This paper argues against the possibility of presenting a consistent version of the Copenhagen Interpretation of Quantum Physics, characterizing its founders' philosophical pronouncements including those on the realism-antirealism issue, as a contingent collection of local, often contradictory, moves in changing theoretical and sociopolitical circumstances. The paper analyzes the fundamental differences of opinion between Bohr and the mathematical physicists, Heisenberg and Born, concerning the foundational doctrine of the “indispensability of classical concepts”, and their related disagreements on “quantum reality.” The paper concludes with an explanation of how the appearance of consensus was achieved despite fundamental disagreements among the proponents. The paper undermines the adequacy of the notion of a general conceptual framework to describe the philosophical endeavors of working scientists.
What is a Species, and What is Not?
Authors: Mayr Ernst
Published: December 2007

I analyze a number of widespread misconceptions concerning species. The species category, defined by a concept, denotes the rank of a species taxon in the Linnaean hierarchy. Biological species are reproducing isolated from each other, which protects the integrity of their genotypes. Degree of morphological difference is not an appropriate species definition. Unequal rates of evolution of different characters and lack of information on the mating potential of isolated populations are the major difficulties in the demarcation of species taxa.
Visual Abductive Reasoning in Archaeology
Authors: Shelley Cameron
Published: December 2007

Biographical studies have shown that visual mental imagery plays a significant role in the conduct of scientific research, particularly in the generation of hypotheses. But the nature of visual mental imagery and its participation in abductive inference is not systematically understood. This paper discusses examples of visual abductive reasoning by archaeologists, analyzing them according to the visual information and the process of inference employed. This work supports the conclusion that visual abduction is useful to scientists under certain conditions and that it is amenable to detailed study.
Believing in Language
Authors: Dwyer Susan , Pietroski Paul M.
Published: December 2007

We propose that the generalizations of linguistic theory serve to ascribe beliefs to humans. Ordinary speakers would explicitly (and sincerely) deny having these rather esoteric beliefs about language—e.g., the belief that an anaphor must be bound in its governing category. Such ascriptions can also seem problematic in light of certain theoretical considerations having to do with concept possession, revisability, and so on. Nonetheless, we argue that ordinary speakers believe the propositions expressed by certain sentences of linguistic theory, and that linguistics can therefore teach us something about belief as well as language. Rather than insisting that ordinary speakers lack the linguistic beliefs in question, philosophers should try to show how these empirically motivated belief ascriptions can be correct. We argue that Stalnaker's (1984) “pragmatic” account—according to which beliefs are dispositions, and propositions are sets of possible worlds—does just this. Moreover, our construal of explanation in linguistics motivates (and helps provide) responses to two difficulties for the pragmatic account of belief: the phenomenon of opacity, and the so-called problem of deduction.
Critical Review: Sober's Philosophy of Biology and his Philosophy of Biology
Authors: Rosenberg Alex
Published: December 2007

An examination of the foundations of Elliot Sober's philosophy of biology as reflected in his introductory textbook of that title reveals substantial and controversial philosphical commitments. Among these are the claim that all understanding is historical, the assertion that there are biological laws but they are necessary truths, the view that the fundamental theory in biology is a narrative, and the suggestion that biology adverts to ungrounded probablistic propensities of the sort to be met with elsewhere only in quantum mechanics.
The Scientist as Child
Authors: Gopnik Alison
Published: December 2007

This paper argues that there are powerful similarities between cognitive development in children and scientific theory change. These similarities are best explained by postulating an underlying abstract set of rules and representations that underwrite both types of cognitive abilities. In fact, science may be successful largely because it exploits powerful and flexible cognitive devices that were designed by evolution to facilitate learning in young children. Both science and cognitive development involve abstract, coherent systems of entities and rules, theories. In both cases, theories provide predictions, explanations, and interpretations. In both, theories change in characteristic ways in response to counterevidence. These ideas are illustrated by an account of children's developing understanding of the mind.
Science and Core Knowledge
Authors: Carey Susan , Spelke Elizabeth
Published: December 2007

While endorsing Gopnik's proposal that studies of the emergence and modification of scientific theories and studies of cognitive development in children are mutually illuminating, we offer a different picture of the beginning points of cognitive development from Gopnik's picture of “theories all the way down.” Human infants are endowed with several distinct core systems of knowledge which are theory-like in some, but not all, important ways. The existence of these core systems of knowledge has implications for the joint research program between philosophers and psychologists that Gopnik advocates and we endorse. A few lessons already gained from this program of research are sketched.
Science as Child's Play: Tales from the Crib
Authors: Fine Arthur
Published: December 2007

Child's play? Certainly Alison Gopnik is in good company in pointing to connections between science and child development. To mention just a few luminaries: in psychology, Freud (followed by Erikson and Piaget) looked at the developmental connection between children's play and adult work; in philosophy, Thomas Reid may have been the first to ground the faculty of reasoning in developmental stages that “unfold themselves by degrees; so that it [the child] is inspired with the various principles of common sense” (1764, V, 7). As for connecting commonsense reasoning and science, according to Einstein, “The whole of science is nothing more than a refinement of everyday thinking” (1954, 290). Quod erat demonstrandum.
The Return of the Group
Authors: Sterelny Kim
Published: December 2007

Once upon a time in evolutionary theory, everything happened for the best. Predators killed only the old or the sick. Pecking orders and other dominance hierarchies minimized wasteful conflict within the group. Male displays ensured that only the best and the fittest had mates. In the culmination of this tradition, Wynne-Edwards (1962, 1986) argued that many species have mechanisms that ensure groups do not over-exploit their resource base. The “central function” of territoriality in birds and other higher animals is “of limiting the numbers of occupants per unit area of habitat” (1986, 6). Species with dominance hierarchies, species with lekking breeding systems, and species with communal breeding regulate their populations. These social mechanisms have population regulation as their “underlying primary function” (1986, 9). Wynne-Edwards argued that these mechanisms evolve through group selection. Populations without such mechanisms are apt to go extinct by eroding their own resource base.
The Evaluation of Psychotherapy: A Reply to Greenwood
Authors: Erwin Edward
Published: December 2007

John Greenwood (this issue) claims that neglect of an important methodological distinction has contributed directly to the “epistemic impoverishment” of empirical studies of all forms of professional psychotherapy. I challenge this claim, as well as other important claims he makes about the efficacy of psychoanalysis and other forms of psychotherapy.
A piezoelectric microvalve for cryogenic applications
Authors: Park Jong M , Taylor Ryan P , Evans Allan T , Brosten Tyler R , Nellis Gregory F , Klein Sanford A , Feller Jeffrey R , Salerno Louis , Gianchandani Yogesh B
Published: December 2007

This paper reports on a normally open piezoelectrically actuated microvalve for high flow modulation at cryogenic temperatures. One application envisioned is to control the flow of a cryogen for distributed cooling with a high degree of temperature stability and a small thermal gradient. The valve consists of a micromachined die fabricated from a silicon-on-insulator wafer, a glass wafer, a commercially available piezoelectric stack actuator and Macor™ ceramic encapsulation that has overall dimensions of 1 × 1 × 1 cm3. A perimeter augmentation scheme for the valve seat has been implemented to provide high flow modulation. In tests performed at room temperature the flow was modulated from 980 mL min−1with the valve fully open (0 V), to 0 mL min−1with a 60 V actuation voltage, at an inlet gauge pressure of 55 kPa. This range is orders of magnitude higher flow than the modulation capability of similarly sized piezoelectric microvalves. At the cryogenic temperature of 80 K, the valve successfully modulated gas flow from 350 mL min−1down to 20 mL min−1with an inlet pressure of 104 kPa higher than the atmosphere. The operation of this valve has been validated at elevated temperatures as well, up to 380 K. The valve has a response time of less than 1 ms and has operational bandwidth up to 820 kHz.
A mathematical model of biological resource dynamics, using Caspian/Ural sturgeon as a case study
Authors: Gabbasov Mars B. , Jaichibekov Nurbolat Zh. , Lebedev Daniel V.
Published: December 2007

Gabbasov, M. B., Jaichibekov, N. Zh., and Lebedev, D. V. 2008. A mathematical model of biological resource dynamics, using Caspian/Ural sturgeon as a case study. – ICES Journal of Marine Science, 65: 103–110. Some of the general principles involved in constructing mathematical models of biological resource dynamics are presented along with some of the requirements of such models for them to have value in terms of management application. A case study of sturgeon population dynamics in the Caspian Basin, using physical and biological parameters, is used to show theoretically how such a model can be developed and applied. The results of the case study are presented in graphic form, and the influence of different processes on the outcome of the calculation is discussed.
Ignoramus, Ignorabimus? On Uncertainty in Ecological Inference
Authors: Elff Martin , Gschwend Thomas , Johnston Ron J.
Published: December 2007

Models of ecological inference (EI) have to rely on crucial assumptions about the individual-level data-generating process, which cannot be tested because of the unavailability of these data. However, these assumptions may be violated by the unknown data and this may lead to serious bias of estimates and predictions. The amount of bias, however, cannot be assessed without information that is unavailable in typical applications of EI. We therefore construct a model that at least approximately accounts for the additional, nonsampling error that may result from possible bias incurred by an EI procedure, a model that builds on the Principle of Maximum Entropy. By means of a systematic simulation experiment, we examine the performance of prediction intervals based on this second-stage Maximum Entropy model. The results of this simulation study suggest that these prediction intervals are at least approximately correct if all possible configurations of the unknown data are taken into account. Finally, we apply our method to a real-world example, where we actually know the true values and are able to assess the performance of our method: the prediction of district-level percentages of split-ticket voting in the 1996 General Election of New Zealand. It turns out that in 95.5% of the New Zealand voting districts, the actual percentage of split-ticket votes lies inside the 95% prediction intervals constructed by our method.
Wolbachiagenome integrated in an insect chromosome: Evolution and fate of laterally transferred endosymbiont genes
Authors: Nikoh Naruo , Tanaka Kohjiro , Shibata Fukashi , Kondo Natsuko , Hizume Masahiro , Shimada Masakazu , Fukatsu Takema
Published: December 2007

Recent accumulation of microbial genome data has demonstrated that lateral gene transfers constitute an important and universal evolutionary process in prokaryotes, while those in multicellular eukaryotes are still regarded as unusual, except for endosymbiotic gene transfers from mitochondria and plastids. Here we thoroughly investigated the bacterial genes derived from aWolbachiaendosymbiont on the nuclear genome of the beetleCallosobruchus chinensis. Exhaustive PCR detection and Southern blot analysis suggested that ∼30% ofWolbachiagenes, in terms of the gene repertoire ofwMel, are present on the insect nuclear genome. Fluorescent in situ hybridization located the transferred genes on the proximal region of the basal short arm of the X chromosome. Molecular evolutionary and other lines of evidence indicated that the transferred genes are probably derived from a single lateral transfer event. The transferred genes were, for the length examined, structurally disrupted, freed from functional constraints, and transcriptionally inactive. Hence, most, if not all, of the transferred genes have been pseudogenized. Notwithstanding this, the transferred genes were ubiquitously detected from Japanese and Taiwanese populations ofC. chinensis, while the number of the transferred genes detected differed between the populations. The transferred genes were not detected from congenic beetle species, indicating that the transfer event occurred after speciation ofC. chinensis, which was estimated to be one or several million years ago. These features of the laterally transferred endosymbiont genes are compared with the evolutionary patterns of mitochondrial and plastid genome fragments acquired by nuclear genomes through recent endosymbiotic gene transfers.
Graphical representation of the diffraction grating equation
Authors: Fortin Gilles
Published: December 2007

The well-known diffraction grating equation can be represented by a simple and useful graph that makes the analysis of the diffraction orders produced by a grating easier. This paper explains the construction of the graph and how to use it with an example.
Physics faculty and educational researchers: Divergent expectations as barriers to the diffusion of innovations
Authors: Henderson Charles , Dancy Melissa H.
Published: December 2007

Physics Education Research (PER) practitioners have engaged in substantial curriculum development and dissemination work in recent years. Yet, it appears that this work has had minimal influence on the fundamental teaching practices of the typical physics faculty. To better understand this situation, interviews were conducted with five likely users of physics education research. All reported making changes in their instructional practices and all were influenced, to some extent, by educational research. Yet, none made full use of educational research and most had complaints about their interactions with educational researchers. In this paper we examine how these instructors used educational research in making instructional decisions and identify divergent expectations about how researchers and faculty can work together to improve student learning. Although different instructors emphasized different aspects of this discrepancy between expectations, we believe that they are all related to a single underlying issue: the typical dissemination model is to disseminate curricular innovations and have faculty adopt them with minimal changes, while faculty expect researchers to work with them to incorporate research-based knowledge and materials into their unique instructional situations. Implications and recommendations are discussed.
Wick calculus
Authors: Wurm Alexander , Berg Marcus
Published: December 2007

In quantum field theory the “normal ordering” of operators is routinely used, which amounts to shuffling all creation operators to the left. Potentially confusing is the occurrence in the literature of normal-ordered functions, sometimes called “Wick transforms.” In this paper, we introduce the reader to some basic results, ideas, and mathematical subtleties about normal ordering of operators and functions. The intended audience are instructors of quantum field theory and researchers who are interested but not specialists in mathematical physics.
The early stages of fungal invasion in Norway spruce infested by the bark beetle Ips typographus
Authors: Solheim Halvor
Published: December 2007

Healthy Norway spruce trees infested by the bark beetle Ips typographus were investigated weekly for 10 weeks to examine the early stages in fungal invasion. The study was performed in southeastern Norway during an epidemic period. The fungal association consisted of Ophiostoma species and an undescribed Graphium species, which invaded the sapwood in an obvious succession. The pathogenic species Ophiostoma polonicum was the first invader of both phloem and sapwood and was always in the leading edge of fungal penetration into sapwood. Ophiostoma bicolor followed O. polonicum in the sapwood invasion. These species were successively replaced by Graphium sp. 1, Ophiostoma penicillatum and Ophiostoma ainoae. Ophiostoma penicillatum seems to be more adapted to colonizing the phloem than the sapwood. The earliest invaders were the species most frequently carried by the beetles. Key words: Norway spruce, Ips typographus, Ophiostoma, fungal succession.
Holocene history of forest trees on the Bruce Peninsula, southern Ontario
Authors: Bennett K. D.
Published: December 2007

Two new pollen sequences from the Bruce Peninsula, southern Ontario, demonstrate the Holocene history of forests in the area. During the mid- and late Holocene, the southern portion of the peninsula supported a rich deciduous forest, dominated by Acer saccharum and Fagus grandifolia, while the northern portion was dominated by a forest with a much higher proportion of conifers. These two sites are compared numerically with a third site, on Manitoulin Island, by means of principal components analysis. Despite similar bedrock, soils, climate, and topography, the three pollen sequences show a remarkable divergence of Holocene forest history. The role of historical factors in determining forest composition may be much greater than previously appreciated. This study emphasises the need to understand the magnitude of variation between pollen sequences within uniform terrain before ascribing the differences in pollen sequences from contrasting environments (because of climate, soils or topography) to the factors causing the obvious contrast. Key words: Holocene forest history, pollen analysis, principal components analysis, Bruce Peninsula, southern Ontario.
Comparative morphology and anatomy of absorbing roots and anchoring roots in three species of Cyclanthaceae (Monocotyledoneae)
Authors: Wilder George J.
Published: December 2007

Asplundia sp., Evodianthus funifer, and Thoracocarpus bissectus are root-climbing lianas that each have absorbing roots and anchoring roots. On stems appressed to the trunks of host trees, both types of roots arise mainly from internodes, generally emerging from those halves of stem surfaces facing the trunks (Asplundia sp., E. funifer), and may form nonreplacement roots and replacement roots. Aerial portions of absorbing roots differ from anchoring roots according to direction of growth, abundance of nonreplacement roots, diameter 1 cm distal to base, length, abundance, and color (T. bissectus). In all species the anchoring roots (with or without replacement roots) are interpretable as determinate because on long specimens their distal portions appear anatomically narrowed and reduced. In contrast, aerial parts of absorbing roots are indeterminate. The determinate aspects of anchoring roots and the general restriction (on stems appressed to tree trunks) of roots to trunk-facing stem surfaces are advantageous as means for conserving biomass. Key words: roots, root morphology, root dimorphism, Cyclanthaceae.
Gluconic acid synthesis by the ectomycorrhizal fungus Tricholoma robustum
Authors: Iwase Koji
Published: December 2007

During mycelial culture of Tricholoma robustum, the medium gradually became acidified to approximately pH 3.9. High performance liquid chromatography showed that gluconic acid was secreted into the culture medium, and the amount of gluconic acid produced was measured by enzymatic analysis. Gluconic acid synthesis by all other related species, Tricholoma matsutake, Tricholoma caligatum, Tricholoma ponderosum, Tricholoma fulvocastaneum, and Tricholoma zelleri was poor, except for Tricholoma bakamatsutake, which showed relatively high productivity. Activity of glucose oxidase, which is responsible for gluconic acid production, was highest in T. robustum and second highest in T. bakamatsutake. The activity in these two species was much higher than those of other species. These results indicate that gluconic acid was synthesized from glucose by glucose oxidase in T. robustum as well as in T. bakamatsutake. Key words: ectomycorrhizal fungi, gluconic acid, glucose oxidase, Tricholoma robustum.
Phenotypic selection in a population of Crepis tectorum ssp. pumila (Asteraceae)
Authors: Andersson Stefan
Published: December 2007

A 3-year demographic study was conducted to reveal targets of selection on morphology and life history in a population of Crepis tectorum ssp. pumila, a winter annual plant confined to calcareous grasslands (alvars) on the Baltic island of Öland (south Sweden). I calculated the selection differential to describe the change in the mean value of a character due to selection and used multiple regression analyses to partition the direct effect of selection on the trait from indirect responses of selection on other traits. Rosette leaf number, a convenient measure of plant size, was strongly correlated with both viability and fertility (fitness). There was also a strong relationship between fitness and the extent to which the plants expressed traits characterizing this particular taxon. Multiple regression analyses indicated direct selection favouring plants with deeply lobed leaves and a densely branched stem, two distinctive traits of ssp. pumila believed to be adaptive in the alvar habitat. Only stem height was subject to both direct and indirect selection in the wrong direction; taller individuals were more successful than those with a shorter stem, a surprising result considering the inferred advantage of a short stature in the exposed alvar habitat. Selection on other traits assumed to be ecologically important (germination time, flowering time, and seed size) was found to be either absent or variable in direction when other traits were held constant. The failure of plants to survive to the flowering stage in the last two summers indicates strong selection for plants that produce a high percentage of dormant seeds. Overall, the contemporary selection regime as revealed by demographic data was only partly congruent with predictions regarding historical selection pressures based on large-scale patterns of variation (ecotypic differentiation). Key words: Crepis tectorum, ecotypic differentiation, life history, morphology, phenotypic selection.
Effects of dehydration and rehydration on the polar lipid and fatty acid composition of Ramonda species
Authors: Stevanovic Branka , Thu Pham Thi Anh , de Paula Fernando Monteiro , da Silva Jorge Vieira
Published: December 2007

Endemic Balkan species Ramonda serbica and Ramonda nathaliae (Gesneriaceae) are rare resurrection flowering plants, known to withstand repeated cycles of desiccation–rehydration in their natural habitat. Analysis of their leaf lipids and fatty acids revealed a rather small amount of total lipids (15.8 mg/g dry weight in R. serbica and 19.5 in R. nathaliae) and galactolipids, particularly the monogalactosyl-diacylglycerol, considerably poorer in linolenic acid in comparison to other flowering plants (55% for R. nathaliae and 64% for R. serbica). Severe desiccation leads to a drastic loss in total lipids (76% in R. serbica and 71.5% in R. nathaliae), especially in monogalactosyl-diacylglycerol, but the recovery is extremely rapid and thorough upon the rewetting. A shift towards the more saturated oleic and linoleic acids in galactolipids occurs at a different time and to a different degree in the two species, and it is not evenly repaired. Ramonda serbica, known to be somewhat less resistant, shows a wider range of lipid changes. Key words: lipid, fatty acids, desiccation-tolerant plants, Ramonda serbica, Ramonda nathaliae.
Studies on Cenococcum geophilum. II. Sclerotium morphology, germination, and formation in pure culture and growth pouches
Authors: Massicotte H. B. , Trappe J. M. , Peterson R. L. , Melville L. H.
Published: December 2007

Cenococcum geophilum sclerotium morphology, germination, and formation in pure culture and growth pouches is described. On agar, germination of most field-collected sclerotia occurred within 30 days. In vitro attempts to initiate sclerotia succeeeded to varying degrees for 20 of the 22 isolates (collected in three main habitats in Oregon) in agar or peat – vermiculite but not in liquid culture. Sclerotium formation was initiated in 1-month-old cultures by branching, lateral growth, and subsequent septation of hyphae. Surface cells of compact hyphae of young sclerotia elongated, became irregularly arranged, and melanized. In growth pouches, sclerotium initials developed on the paper wick from a hyphal mat formed from convoluted hyphae. Mature sclerotia appeared as small spherical structures with linear hyphae radiating out from the surface. Sections revealed a well-differentiated rind and a medulla with pseudoparenchymatous organization. Numerous nuclei and vacuoles were distributed in both rind and medullary hyphae. Key words: Cenococcum, sclerotium, initiation, in vitro.
Early patterns of revegetation of artificial earthen mounds in a northern mixed prairie
Authors: Umbanhowar Jr. Charles E.
Published: December 2007

Patches of bare soil are thought to be important to the diversity and structure of North American grasslands. In 1987, 45 7.5-dm diameter artificial earthen mounds were built in low-, mid-, and high-prairie types to experimentally study the effects of mound location on patterns of mound revegetation. Stem densities and species abundance data were recorded every other week during the summers of 1987 and 1988. Few stems were recorded in 1987, and stem density more than quadrupled in 1988, but less than 1 % of all stems were seedlings. Grass stem densities were significantly higher on low-prairie mounds than mid- or high-prairie mounds and were concentrated in the outer perimeter of mounds. Forb stem densities did not vary significantly between prairie types or on-mound position. Mound species composition closely resembled surrounding vegetation, reflecting between and within prairie-type compositional variation. Key words: colonization, disturbance, earthen mounds, northern mixed prairie, patch, revegetation.
Observations on the in situ detection of free radicals in leaves using electron paramagnetic resonance spectrometry
Authors: Runeckles Victor C. , Vaartnou Manivalde
Published: December 2007

To follow in situ changes in free radicals in leaves subjected to changes in the composition of the surrounding air, a system has been developed for obtaining X-band (9 GHz) electron paramagnetic resonance (EPR) spectra of intact leaf tissue over extended periods. Studies with radish (Raphanus sativus), bluegrass (Poa pratensis), and ryegrass (Lolium perenne) leaves in darkness or illuminated with 650 nm, 710 nm, or white light in the spectrometer cavity readily reveal the photosynthetic signals I and II, and signals attributable to Mn2+ and Fe3+. Detached pieces of leaf cannot be used after about 1 h in the cavity because of the appearance of a large EPR signal resulting from excision. However, attached leaves of the grasses can be maintained in a fully functioning state in the cavity for several days, or can be withdrawn and replaced at will. Plants grown in high photon influx densities were found to reveal a large free radical signal, related to photoinhibition, that masks the typical photosynthetic signals but that can usually be eliminated by subjecting the tissue to 9 GHz microwave radiation. Signal changes in response to changes in the composition of the air stream can be directly tracked over extended periods, provided that no major changes occur in the underlying Mn2+ or Fe3+ signals. Preliminary studies with the air pollutants, sulphur dioxide, and ozone have demonstrated the potential of the system for revealing changes in the photosynthetic and other EPR signals resulting from the uptake of such phytotoxic gases. Key words: free radical, electron paramagnetic resonance spectrometry, intact leaf tissue, photosystem, air pollution, stress.
Relationships of Populus × acuminata and Populus × generosa with their parental species examined by gas chromatography – mass spectrometry of bud exudates
Authors: Greenaway W. , English S. , Whatley F. R.
Published: December 2007

Analysis by gas chromatography – mass spectrometry of bud exudates of Populus deltoides and Populus trichocarpa showed that they each contained a number of different compounds. Exudates of P. trichocarpa contained dihydrochalcones and sesquiterpenols, which were absent from the exudate of P. deltoides, but lacked the flavones, flavanones, and flavanonols present in the exudate of P. deltoides. Exudates of their hybrid, P. × generosa (P. × interamericana), contained compounds typical of both parent plants. Bud exudates of Populus angustifolia and Populus sargentii were qualitatively similar in their flavonoid composition but the exudate of P. angustifolia contained in addition caffeate esters, which were absent from P. sargentii. The exudate from the hybrid P. × acuminata was intermediate. Bud exudates of P. angustifolia and P. × acuminata were more like those of P. deltoides and P. sargentii (section Aigeiros) than they were to those of P. trichocarpa (section Tacamahaca). It is therefore suggested that P. angustifolia and P. × acuminata might be more correctly classified together with P. sargentii and P. deltoides within the section Aigeiros. Key words: Populus, bud exudate, chemotaxonomy, gas chromatography – mass spectrometry.
Multinucleate condition of Puccinia striiformis in colonies isolated from infected wheat leaves with macerating enzymes
Authors: Chong J. , Kang Z. , Kim W. K. , Rohringer R.
Published: December 2007

A fluorescence microscopy study was carried out to examine the multinuclear condition in parasitic colonies of one isolate of Puccinia striiformis in leaf tissue of a susceptible wheat. At 5 and 10 days after inoculation, colonies were isolated with macerating enzymes and sequentially stained with 4′-6-diamidino-2-phenylindole and Calcofluor for nuclear counts in the intercellular hyphal cells, haustorium mother cells, and urediniospores. In 10-day-old colonies, more than 98% of the hyphal cells located adjacent to the uredinia were binucleate. Elsewhere in the colonies, the hyphal cells were highly variable in nuclear number; approximately 20% contained two nuclei, 18% contained four, 26% contained six, and 28% contained eight. In 5-day-old colonies, the hyphal cells were also highly variable in nuclear number, regardless of where they were located in the colony. The nuclear condition of haustorium mother cells was less variable; the majority contained either two or four nuclei. All urediniospores examined were binucleate. In the parasitic state, the multinucleate condition apparently occurs only in P. striiformis and not in other cereal rust fungi. Key words: multinucleate condition, stripe rust, Puccinia striiformis, DAPI, Calcofluor.
BRANE/ANTIBRANE CONFIGURATIONS IN TYPE IIA AND M-THEORY
Authors: MARSANO JOSEPH
Published: December 2007

We investigate the relation between large N duality applied to systems of D5's and [Formula: see text]'s wrapping vanishing cycles of local CY in type IIB and M-theory lifts of the NS5/D4/[Formula: see text] systems in type IIA to which they are related by T-duality. Through a simple example based on a local CY constructed using an A2 singularity, we review this well-known correspondence in the supersymmetric setting and describe the manner in which it generalizes when antibranes are added. Agreement between the IIB and IIA pictures, which supports the assertion that [Formula: see text] supersymmetry is spontaneously broken in these systems at string tree level, is demonstrated when gs ≪ 1. Novel nonholomorphic features can arise away from this regime and their physical origin is discussed. This note is based on talks given at KITP, Harvard University, TIFR, the University of Tokyo at Hongo, the 2007 Les Houches Summer School, and the 2007 Simons Workshop, is based on work done in collaboration with K. Papadodimas and M. Shigemori, and contains some previously unpublished results.
Q & A EXPERIMENT TO SEARCH FOR VACUUM DICHROISM, PSEUDOSCALAR–PHOTON INTERACTION AND MILLICHARGED FERMIONS
Authors: CHEN SHENG-JUI , MEI HSIEN-HAO , NI WEI-TOU
Published: December 2007

A number of experiments are underway to detect vacuum birefringence and dichroism — PVLAS, Q & A, and BMV. Recently, PVLAS experiment has observed optical rotation in vacuum by a magnetic field (vacuum dichroism). Theoretical interpretations of this result include a possible pseudoscalar–photon interaction and the existence of millicharged fermions. Here, we report the progress and first results of Q & A (QED [quantum electrodynamics] and Axion) experiment proposed and started in 1994. We use a 3.5-m high-finesse (around 30,000) Fabry–Perot prototype detector extendable to 7-m with the cavity mirrors suspended using X-pendulum-double pendulums. To polarize the vacuum, we use a 2.3-T dipole permanent magnet rotated at 5–10 rev/s, with 27-mm-diameter clear borehole and 0.6-m field length. Our ellipsometer/polarization-rotation-detection-system is formed by a pair of Glan–Taylor type polarizing prisms with extinction ratio lower than 10-8together with a polarization modulating Faraday Cell with/without a quarter wave plate. Our first results give (-0.2 ± 2.8) × 10-13rad/pass with 18,700 passes through a 2.3 T 0.6 m long magnet for vacuum dichroism measurement. We present our experimental limit on pseudo-scalar-photon interaction and millicharged fermions.
NEW SUPERSTRING ISOMETRIES AND HIDDEN DIMENSIONS
Authors: POLYAKOV DIMITRI
Published: December 2007

We study the hierarchy of hidden space–time symmetries of noncritical strings in RNS formalism, realized nonlinearly. Under these symmetry transformations the variation of the matter part of the RNS action is canceled by that of the ghost part. These symmetries, referred to as the α-symmetries, are induced by special space–time generators, violating the equivalence of ghost pictures. We classify the α-symmetry generators in terms of superconformal ghost cohomologies Hn ~ H-n-2(n≥0) and associate these generators with a chain of hidden space–time dimensions, with each ghost cohomology Hn ~ H-n-2 "contributing" an extra dimension. Namely, we show that each ghost cohomology Hn ~ H-n-2 of noncritical superstring theory in d-dimensions contains d+n+1 α-symmetry generators and the generators from Hk ~ H-k-2, 1≤k ≤n, combined together, extend the space–time isometry group from the naive SO (d, 2) to SO (d+n, 2). In the simplest case of n = 1 the α-generators are identified with the extra symmetries of the 2T-physics formalism, also known to originate from a hidden space–time dimension.
EXISTENCE OF STRONG TRACES FOR QUASI-SOLUTIONS OF MULTIDIMENSIONAL CONSERVATION LAWS
Authors: PANOV E. YU.
Published: December 2007

We consider a conservation law in the domain Ω ⊂ ℝn+1 with C1 boundary ∂Ω. For a wide class of functions including generalized entropy sub- and super-solutions, we prove the existence of strong traces for normal components of the entropy fluxes on ∂Ω. Non-degeneracy conditions on the flux are not required.
ON A CONJECTURE OF MCINTOSH REGARDING LP-SEQUENCES
Authors: MOSHE YOSSI
Published: December 2007

A sequence [Formula: see text] over ℤ is an LP-sequence if for every prime p and integer n ≥ 0 we have [Formula: see text] (mod p), when [Formula: see text] is a base p expansion of n. In this paper, we study sequences [Formula: see text] such that both [Formula: see text], [Formula: see text] are LP-sequences for some d ≥ 2. One of those sequences is a counter-example to a conjecture of McIntosh [15].
Mendelian Genetics of Apomixis in Plants
Authors: Ozias-Akins Peggy , van Dijk Peter J.
Published: December 2007

Apomixis, asexual reproduction through seeds, has the potential to revolutionize agriculture if its genetic basis can be elucidated. However, the genetic control of natural apomixis has remained obscure until quite recently, owing to all the complications of Mendelian genetics, such as epistatic gene interactions, components that are expressed sporophytically and gametophytically, expression modifiers, polyploidy, aneuploidy, segregation distortion, suppressed recombination, etc., that seem to have accumulated during the evolution of apomixis. In this review we show how molecular markers and superior phenotypic methods have been used to clarify the genetics of apomixis in monocots as well as dicots during the past 15 years. Many of the complexities in the genetics of apomixis are likely secondary and have evolved as a consequence of the reproductive process. New mapping techniques, such as comparative mapping, linkage disequilibrium mapping, and deletion mapping, and new high-throughput sequencing methods, will help to penetrate the core of apomixis chromosomal regions. If the evolutionary genetic load can be exposed and removed, the apomixis genes may be used in agriculture as a tool to fix elite genotypes.
Mammalian Meiotic Recombination Hot Spots
Authors: Arnheim Norman , Calabrese Peter , Tiemann-Boege Irene
Published: December 2007

Our understanding of the details of mammalian meiotic recombination has recently advanced significantly. Sperm typing technologies, linkage studies, and computational inferences from population genetic data have together provided information in unprecedented detail about the location and activity of the sites of crossing-over in mice and humans. The results show that the vast majority of meiotic recombination events are localized to narrow DNA regions (hot spots) that constitute only a small fraction of the genome. The data also suggest that the molecular basis of hot spot activity is unlikely to be strictly determined by specific DNA sequence motifs in cis. Further molecular studies are needed to understand how hot spots originate, function and evolve.
Systems Biology of Caulobacter
Authors: Laub Michael T. , Shapiro Lucy , McAdams Harley H.
Published: December 2007

The dynamic range of a bacterial species’ natural environment is reflected in the complexity of its systems that control cell cycle progression and its range of adaptive responses. We discuss the genetic network and integrated three-dimensional sensor/response systems that regulate the cell cycle and asymmetric cell division in the bacterium Caulobacter crescentus. The cell cycle control circuitry is tied closely to chromosome replication and morphogenesis by multiple feedback pathways from the modular functions that implement the cell cycle. The sophistication of the genetic regulatory circuits and the elegant integration of temporally controlled transcription and protein synthesis with spatially dynamic phosphosignaling and proteolysis pathways, and epigenetic regulatory mechanisms, form a remarkably robust living system.
Thermal Decomposition Mechanism of Formed and Cycled Lead Dioxide Electrodes and Its Relationship to Capacity Loss and Battery Failure
Authors: Caulder S. M. , Simon A. C.
Published: December 2007

The structural changes accompanying capacity loss in the

PbO

2

/

PbSO

4

electrode were followed using differential thermal analysis. The thermal decomposition mechanism of formed plates was found to differ, depending on the method of manufacture. All cycled plates, however, gave the same decomposition mechanism after a few cycles. The major changes in the DTA curves, as the positive electrode was cycled to failure, was the gradual disappearance of the exothermic peak at 200°C and the endothermic peak at 358°C. It is believed that these peaks are associated with an electrochemically active amorphous form of

PbO

2

. As the electrochemically active

PbO

2

is cycled to failure it is converted to an electrochemically inactive form of

PbO

2

. This latter form of

PbO

2

gives DTA results similar to those obtained on reagent

PbO

2

. The continual conversion of electrochemically active

PbO

2

to the electrochemically inactive

PbO

2

is one of the major factors that accounts for the loss in battery capacity and ultimate failure.
Effects of Diffusion on Aluminum Depletion and Degradation of NiAl Coatings
Authors: Smialek James L. , Lowell Carl E.
Published: December 2007

Experiments were performed to critically demonstrate the effects of diffusion on the aluminum depletion and degradation of

NiAl

coatings on superalloys. Pack aluminized IN 100 and Mar‐M200 were diffusion annealed in

5
×
10

−

3

Torr vacuum at 1100°C for 300 hr. Aluminum losses due to oxidation and vaporization were minimal. Metallographic and electron microprobe analyses showed considerable interdiffusion of the coating with the substrate, which caused a large decrease in the original aluminum level of the coating. Subsequent cyclic furnace oxidation tests were performed at 1100°C using 1 hr cycles on prediffused and as‐coated specimens. The prediffusion treatment decreased the oxidation protection for both alloys, but more dramatically for IN 100. Identical oxidation tests of bulk

NiAl

, where such diffusion effects are precluded, showed no signs of degradation at twice the time needed to degrade the coated superalloys. These results, plus limited tests showing the reduced oxidation resistance of aluminum‐poor

NiAl

, suggest a degradation model whereby the coating is first depleted of aluminum by diffusion, as opposed to

Al

2

O

3

spalling, then rapidly degraded by the formation of spallprone oxides.
Dielectric Breakdown Properties of SiO2 Films Grown in Halogen and Hydrogen‐Containing Environments
Authors: Osburn C. K.
Published: December 2007

Thermal oxidation of silicon, in the presence of chlorine or bromine compounds, effectively improved the dielectric breakdown characteristics (as measured with a voltage ramp) of the resulting

SiO

2

films. At high halogen concentrations the oxidation rate was erratic; the optimal initial breakdown properties were attained by oxidizing with about one‐half of the halogen‐containing additive that would cause etching of the Si. Oxidation in the presence of halides increased the resistance of

SiO

2

films to dielectric breakdown under accelerated bias‐temperature stressing. The maximum time to failure varied semilogarithmically with

HCl

concentration and increased by 0.3 to 0.65 decade per per cent of

HCl

(0–3%

HCl

range) for applied fields from 2 to 7 MV/cm, respectively. Higher oxidation temperatures further improved the resistance of

HCl

oxides to dielectric wear‐out. The longer wear‐out times were attributed to hydrogen rather than the halogen and could be achieved by oxidation in small concentrations of

H

2

O

, annealing in H2, or.implantation of H2 or

H

2

O

.
Native Oxide Mask for Zinc Diffusion in Gallium Arsenide
Authors: Spitzer S. M. , Schwartz B. , Weigle G. D.
Published: December 2007

This paper reports the first use of an amorphous native oxide on gallium arsenide to mask against zinc diffusion. Anodic oxides were grown at low temperature (≤100°C), and stripes were defined in this oxide using standard photolithographic processing. These samples were diffused, after an appropriate annealing cycle, in a closed system using a zinc source

(

Zn

3

As

2

+
GaAs
)

at 612°C for times up to 2 hr. Diffusion depths were measured using a lap and stain procedure, and the results showed the oxide to be effective as a zinc barrier. Furthermore, no anomalous lateral underdiffusion was observed indicative of a high integrity interface between the oxide and semiconductor.