bluuebunny/crossref_metadata_2025 huggingface dataset:
Pop-ups and related damage in granite at the Medika Pluton in southeastern Manitoba
Authors: Everitt Richard A.
Published: August 2009

Stress relief in the form of small displacements and a pop-up has occurred in a line-drilled, blast-free quarry in Archean granite 100 km east of Winnipeg. A 60 m by 19 m and up to 1.5 m thick block, forming the east wall of the quarry, has undergone deformation and displacement following quarrying. The pop-up base is a low-dipping exfoliation fracture that predates the quarry. Block movement is complex, with compressional, strike-slip, and extensional features observed around the damaged zone perimeter. Overall, block displacement and expansion are dominated by upslope thrusting. The northeast–southwest displacement of the postexcavation damage zone mimics that of a nearby pre-quarry pop-up. The orientation of the maximum horizontal in situ compressive stress, σh max, inferred from the postquarry pop-up is consistent with on-site overcoring results. The compressional origin of the quarry-induced low-dip thrust fault and pop-up and the predominant orientations of these structures are compatible with the ambient stress field in eastern North America. This indicates that, although the quarry initiated and localized the damage zone, the regional in situ stress field defines its geometry and relative displacement.
Experiments for alternative management of forest reserves: effects of partial cutting on stem growth and mortality of large oaks
Authors: Götmark Frank
Published: August 2009

Although protected forests are usually kept as free of human disturbance as possible, careful cutting may favour biodiversity in such areas. However, the use of heavy machinery during cutting operations may have a negative impact on protected forests. The large oaks ( Quercus spp.) found in many temperate nature reserves have a rich associated biodiversity. In 25 conservation forests in Sweden, the basal area growth and mortality of 250 large oaks (31–110 cm DBH) were compared between plots that were partially cut to promote the growth and survival of oaks and undisturbed plots. Each forest had one treatment plot (1 ha) and one undisturbed reference plot (1 ha) with similar levels of canopy cover. In 2002–2003, about 25% of the basal area was harvested in treatment plots, thereby increasing canopy openness from 14% to 33%. Cutting increased the mean relative basal area growth of large oaks (49% by plot, 22% by tree) after four seasons (P = 0.026). However, in nine forests, the growth rate was not higher in the treated plot than in the reference plot. Mortality, apparently due to cutting, was recorded only in one forest, where 18 large oaks died. Tree condition (percentage of dead large branches in crown) was the best (negative) predictor of growth rate, and openness around oak crown was also a (positive) predictor. Partial cutting favoured the growth of oaks and may be recommended, but a “hands-off” policy is also effective for these conservation forests.
Biases in the estimation of size-dependent mortality models: advantages of a semiparametric approach
Authors: Vieilledent Ghislain , Courbaud Benoît , Kunstler Georges , Dhôte Jean-François , Clark James S.
Published: August 2009

Mortality rate is thought to show a U-shape relationship to tree size. This shape could result from a decrease of competition-related mortality as diameter increases, followed by an increase of senescence and disturbance-related mortality for large trees. Modeling mortality rate as a function of diameter is nevertheless difficult, first because this relationship is strongly nonlinear, and second because data can be unbalanced, with few observations for large trees. Parametric functions, which are inflexible and sensitive to the distribution of observations, tend to introduce biases in mortality rate estimates. In this study we use mortality data for Abies alba Mill. and Picea abies (L.) Karst. to demonstrate that mortality rate estimates for extreme diameters were biased when using classical parametric functions. We then propose a semiparametric approach allowing a more flexible relationship between mortality and diameter. We show that the relatively shade-tolerant A. alba has a lower annual mortality rate (2.75%) than P. abies (3.78%) for small trees (DBH <15 cm). Picea abies, supposedly more sensitive to bark beetle attacks and windthrows, had a higher mortality rate (up to 0.46%) than A. alba (up to 0.30%) for large trees (DBH ≥50 cm).
A geostatistical approach to optimize sampling designs for local forest inventories
Authors: Hernández Jaime , Emery Xavier
Published: August 2009

In forest management, it is of interest to obtain detailed inventories such that the local prediction errors on forest attributes are less than a prespecified threshold, while keeping the number of ground samples as low as possible. Given an initial sampling design, we propose an algorithm to determine the additional sample locations. The algorithm relies on two tools: geostatistical simulation, which allows measuring the uncertainty in the values of the attribute of interest, and simulated annealing, which allows finding an infill design that minimizes a given objective function. The proposed approach is applied to a data set from a Prosopis spp. plantation located in the Atacama Desert, in which the measured attribute is the rate of tree survival.
Integration of soil moisture, xylem water potential, and fall–spring herbicide treatments to achieve the maximum growth response in newly planted Douglas-fir seedlings
Authors: Dinger Eric J. , Rose Robin
Published: August 2009

Early in the establishment of Pacific Northwest Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) plantations, herbaceous vegetation can decrease seedling growth through competition for soil moisture during the dry summer months. This study was designed to statistically quantify soil moisture, seedling xylem water potential (Ψ), vegetation community, and seedling growth response to six herbicide treatment regimes commonly applied over the first 2 years of establishment. When compared with the control, soil moisture and seedling Ψ increased in response to reductions in competitive cover, allowing seedlings to extend productive growing time from 28 to 80 days. As a result, seedling volume growth increased from 56 cm3 in the untreated control to greater than 250 cm3 for the most intensive herbicide treatment regimes. Vegetation surveys revealed that treatment regimes had the potential to provide a disturbance, which could shift community composition from native to introduced species as the relationship decreased from 10:1 to 2:1. The most intense herbicide treatment regime reduced cover below 20%, retained soil moisture >30%, maintained predawn seedling Ψ above –1.0 MPa, and decreased height to diameter ratio below 50, increasing the likelihood of successful plantation establishment.
Light availability and soil source influence ectomycorrhizal fungal communities on oak seedlings grown in oak- and hemlock-associated soilsContribution No. 225 of the Louis Calder Center and Biological Station, Fordham University, Armonk, New York.
Authors: Turner Gregory D. , Lewis J.D. , Mates-Muchin J.T. , Schuster William F. , Watt Laura
Published: August 2009

Forests exhibit spatial heterogeneity in plant composition and light, which may influence ectomycorrhizal fungal (ECM) communities. We investigated whether light and soil source affect ECM colonization and community properties on red oak ( Quercus rubra L.) seedlings. Seedlings were grown under 10%, 45%, and full sunlight in soils removed beneath red oak and eastern hemlock ( Tsuga canadensis (L.) Carr.) trees. Between soils, colonization and diversity were significantly greater in intermediate–high versus low light. Across light levels, colonization, richness, and diversity were greater on seedlings grown in oak versus hemlock soils. The frequency of seedlings colonized by three of the four most common morphotypes was more responsive to light in oak versus hemlock soil. Colonization differences between soil sources were associated with differences in richness, which may in turn reflect host specificity and fine root length differences. Increasing colonization with increasing light was associated with increased richness, which in turn may reflect increased carbon allocation to roots. Results suggest that differences in responses of individual ECM morphotypes coupled with host responses to light and soil source may influence ECM colonization and diversity. Changes in ECM colonization and diversity could in turn affect seedling recruitment, especially for seedlings encountering variable light regimes and host species.
Altitudinal differentiation in growth and phenology among populations of temperate-zone tree species growing in a common garden
Authors: Vitasse Yann , Delzon Sylvain , Bresson Caroline C. , Michalet Richard , Kremer Antoine
Published: August 2009

The aim of the study was to determine whether there are genetic variations in growth and leaf phenology (flushing and senescence) among populations of six woody species ( Abies alba Mill., Acer pseudoplatanus L., Fagus sylvatica L., Fraxinus excelsior L., Ilex aquifolium L., and Quercus petraea (Matt.) Liebl.) along altitudinal gradients, using a common-garden experiment. We found (i) significant differences in phenology and growth among provenances for most species and (ii) evidence that these among-population differences in phenology were related to the annual temperature at the provenance sites for ash, beech, and oak. It is noteworthy that along the same climatic gradient, species can exhibit opposing genetic clines: beech populations from high elevations flushed earlier than those from low elevations, whereas we observed the opposite trend for ash and oak. For most species, significant altitudinal clines for growth were also revealed. Finally, we highlighted the fact that both phenology timing and growth rate were highly consistent from year to year. The results demonstrated that despite the proximity of the populations in their natural area, differences in altitude led to genetic differentiation in their phenology and growth. These adaptive capacities acting along a natural climatic gradient could allow populations to cope with current climate change.
Incorporation of preferential uncertainty into interval-scale priority functions — a case of multicriteria forestry decision making
Authors: Leskinen Pekka , Pykäläinen Jouni , Haara Arto
Published: August 2009

Quantitative decision analysis and respective planning models offer many benefits in forest planning. They are efficient, quick, inexpensive, objective, and repeatable. However, quantitative planning and the respective planning models also include many sources of uncertainty. In this paper our research objective is to analyse decision makers’ preferential uncertainty in the context of multicriteria forestry decision making by using statistical models for so-called interval-scale continuous decision problems. The models are based on 0–1-type utility functions by applying a Finnish school grading system for collecting the preference data. The basic idea is to assess the preferences at some discrete points and then estimate the continuous priority function according to the statistical estimation techniques. An interactive approach for reducing the preferential uncertainty included in the priority model is also developed. In the interactive step, the improvements of the priority model are based on uncertainty measures related to local and (or) global priority models. The role of statistical uncertainty analysis is to make the interactive planning process more efficient and reliable. The interactive and statistical approaches complement each other and promote decision makers’ learning.
Current and future trends in juvenile wood density for coastal Douglas-fir
Authors: Stoehr M.U. , Ukrainetz N.K. , Hayton L.K. , Yanchuk A.D.
Published: August 2009

Increment cores from 10 full-sib families in each of three planting series were collected on 22 test sites per series (a total of 7063 samples across 63 sites). Juvenile wood density for individual test sites ranged from 0.378 to 0.481. Stepwise multiple linear regression analysis with wood density as the dependent variable and a battery of annual and monthly climate variables as independent variables was used to model the current distribution of wood density across the landscape in coastal British Columbia. Differences in the average temperature between the coldest month and the warmest month, precipitation in July, and the mean annual precipitation were the only significant variables predicting wood density, accounting for 47% of the total variation across all sites. Using two future climate change models (CGCM2 A2x and HADCM3 A2x) to predict changes in the three climate variables, wood density was mapped. Wood density will be reduced generally in the present range of coastal Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco var. menziesii ), especially on southern Vancouver Island and along the coastlines of southern British Columbia. This may have implications for the future utility of Douglas-fir as a structural wood species, as well as for breeding and deployment.
Monoterpene persistence in the sapwood and heartwood of longleaf pine stumps: assessment of differences in composition and stability under field conditions
Authors: Eberhardt Thomas L. , Sheridan Philip M. , Mahfouz Jolie M.
Published: August 2009

Monoterpenes in exudates, phloem, and sapwood have received considerable attention relative to the active defenses of pine trees. However, little is known about the composition and function of the heartwood monoterpenes. To address this deficiency, monoterpene contents and relative compositions were determined for sapwood and heartwood samples from longleaf pine ( Pinus palustris Mill.) stumps monitored in the field for a 1 year period postharvest. Gas chromatography – mass spectrometry analysis of sapwood and heartwood sample extracts showed the total monoterpene contents for both declined at essentially the same rate. For sapwood, α-pinene continued to comprise about 75% of all compounds detected, while the proportion of β-pinene declined with time (15%–7%). For the heartwood, lower proportions of both α- and β-pinenes (64% and 10%, respectively) were offset by higher proportions of other monoterpenes (e.g., limonene, α-terpineol, borneol). The low proportion of β-pinene in very old turpentine and lightwood stump samples further suggested the lower stability of this particular monoterpene. While it has not been specifically demonstrated that the monoterpenes have an active role in the decay resistance of longleaf pine stump heartwood, these compounds do persist for a very long time and thus are available should they serve this function.
Rapid capture of growing space by red maple
Authors: Fei Songlin , Steiner Kim C.
Published: August 2009

Red maple ( Acer rubrum L.) is becoming increasingly dominant in forest stands throughout the eastern United States. To investigate the reasons for the increase, we examined the development of red maple and oak ( Quercus spp.) seedlings and stump sprouts following the harvest of oak-dominated stands. Within 7 years after harvest, red maple seedlings were present in far greater numbers and captured more growing space than all oaks combined. Growing space occupied by red maple stump sprouts exceeded oak sprouts by a ratio of 3.5:1. Through stump sprouts alone, red maple fully recaptured the amount of growing space it had previously occupied in the overstory 7 years after harvest. Results from similar but older stands show that red maple dominance is sustained into the third decade of stand development. Red maple surpassed all oaks combined in rapid site capture through both seed-origin and sprout-origin regeneration. Red maple’s superior ability to regenerate by sprouts is particularly favored by timber harvesting following a history of management and disturbance regimes that permit the accumulation of suppressed small-diameter red maple stems. Among the events and processes that promote stand conversion, timber harvesting may be the major proximal cause of the widespread, increasing dominance of red maple.
Seasonal fluctuation of root carbohydrates in hybrid aspen clones and its relationship to the sprouting efficiency of root cuttings
Authors: Stenvall N. , Piisilä M. , Pulkkinen P.
Published: August 2009

We examined the relationship between root carbohydrates and sprouting efficiency in four hybrid aspen ( Populus tremula × Populus tremuloides ) clones. Our hypothesis was that the interclonal variation in sprouting efficiency is due to the concentration of carbohydrates. In addition to that relationship, we wanted to study seasonal fluctuation of carbohydrates and how the –18 °C storage conditions of stock plants affects the stability of carbohydrate content and thus sprouting ability of roots cuttings. Clones varied in root carbohydrate content, and sucrose showed the greatest variation throughout the year. Sucrose levels were highest in the clone with the highest sprouting efficiency and lowest in the clone with the lowest sprouting efficiency. Carbohydrate concentrations were highest in winter and lowest in early autumn. In general, root cuttings sprouted most efficiently when root carbohydrate levels peaked. Although root cuttings taken from frozen (–18 °C) stock plants sprouted poorly in summer and autumn, they had high and almost constant carbohydrate concentrations throughout the year.
Dissolved carbon and nitrogen leaching following variable logging-debris retention and competing-vegetation control in Douglas-fir plantations of western Oregon and Washington
Authors: Slesak Robert A. , Schoenholtz Stephen H. , Harrington Timothy B. , Strahm Brian D.
Published: August 2009

We examined the effect of logging-debris retention and competing-vegetation control (CVC, initial or annual applications) on dissolved organic carbon (DOC), dissolved organic nitrogen, and nitrate-N leaching to determine the relative potential of these practices to contribute to soil C and N loss at two contrasting sites. Annual CVC resulted in higher soil water nitrate-N concentration and flux, with the magnitude and duration of the effect greatest at the high-N site. Most of the increase in nitrate-N at the low-N site occurred in treatments where logging debris was retained. Dissolved organic nitrogen increased at the high-N site in March of each year following annual CVC, but the contribution of this increase to total N concentration was small (2%–4% of total N flux). There was no effect of logging-debris retention or CVC treatment on soil water DOC concentrations, indicating that DOC inputs from logging debris and competing vegetation were either retained or consumed in the mineral soil. The estimated increase in leaching flux of dissolved C and N associated with the treatments was low relative to total soil pools, making it unlikely that loss of these elements via leaching will negatively affect future soil productivity at these sites.
Microfungus communities of Japanese beech logs at different stages of decay in a cool temperate deciduous forest
Authors: Fukasawa Yu , Osono Takashi , Takeda Hiroshi
Published: August 2009

Fallen logs of Japanese beech ( Fagus crenata Blume) at various stages of decomposition were sampled from a cool temperate deciduous forest in Japan and studied for differences in the associated microfungus communities. Wood samples were directly plated onto each of two different media for the identification of fungal species. Approximately 1500 isolations were made, which represent 96 species of filamentous microfungi, consisting of 16 zygomycetes and 80 anamorphic ascomycetes. The number of species per log (α-diversity) increased with log decomposition, while dissimilarity of species composition among logs (β-diversity) showed a unimodal response with the optimum at the intermediate decay stage. The water content and nitrogen concentration of the wood were positively correlated, while the lignocellulose index and relative density were negatively correlated with α-diversity. Stepwise regression models suggested that lignocellulose index was the single most important determinant of variation in α-diversity and explained 31% of variation. Eighteen fungal species frequently isolated from the logs were classified into four groups based on their occurrence patterns. These groups occurred successively during log decomposition, and the succession in early stage of log decomposition was related with relative density, while the succession in late stage was related with water content and nitrogen concentration of wood.
Conifer seed predation in harvested and burned dry Douglas-fir forests in southern British Columbia
Authors: Huggard David J. , Arsenault André
Published: August 2009

Consumption of seeds of Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) and ponderosa pine ( Pinus ponderosa Dougl. ex P. & C. Laws.) was measured in dry Douglas-fir forest at the Opax Mountain Silvicultural Systems site and a nearby burned area as one component of understanding limited natural regeneration in these sites. Seeds were placed in plots surrounded by a physical barrier to invertebrates, enclosed in mesh impermeable to small mammals, covered by litter, or unprotected in clear-cut, partially harvested, uncut, and burned areas and monitored for three several-day sessions in 2 years. Daily survival rates of unprotected seeds of both species were equally low: 0.63 in uncut forest, 0.45 in partially harvested and clear-cut sites, and 0.03 in the burned area. Experimental reductions of coarse woody debris reduced seed predation moderately in patch cuts but not in uncut forest. Litter cover or selective exclosure of ground-dwelling invertebrates reduced seed losses only slightly, whereas small mammal exclosures eliminated most seed loss. Deer mice ( Peromyscus maniculatus Wagner) are likely the most important seed predators. High rates of seed predation in dry Douglas-fir forests likely limit natural regeneration in harvested and burned stands.
THE NON-RELATIVISTIC LIMIT OF THE EULER–NORDSTRÖM SYSTEM WITH COSMOLOGICAL CONSTANT
Authors: SPECK JARED
Published: August 2009

In this paper, we study the singular limit c → ∞ of the family of Euler–Nordström systems indexed by the parameters κ2 and c[Formula: see text], where κ2 > 0 is the cosmological constant and c is the speed of light. Using Christodoulou's techniques to generate energy currents, we develop Sobolev estimates that show initial data belonging to an appropriate Sobolev space launch unique solutions to the [Formula: see text] system that converge to corresponding unique solutions of the Euler–Poisson system with the cosmological constant κ2 as c tends to infinity.
SU(3)-GOODMAN–DE LA HARPE–JONES SUBFACTORS AND THE REALIZATION OF SU(3) MODULAR INVARIANTS
Authors: EVANS DAVID E. , PUGH MATHEW
Published: August 2009

We complete the realization by braided subfactors, announced by Ocneanu, of all SU(3)-modular invariant partition functions previously classified by Gannon.
SINGULAR SPECTRUM FOR RADIAL TREES
Authors: BREUER JONATHAN , FRANK RUPERT L.
Published: August 2009

We prove several results showing that absolutely continuous spectrum for the Laplacian on radial trees is a rare event. In particular, we show that metric trees with unbounded edges have purely singular spectrum and that, generically (in the sense of Baire), radial trees have purely singular continuous spectrum.
BP NEURAL NETWORK-BASED EFFECTIVE FAULT LOCALIZATION
Authors: WONG W. ERIC , QI YU
Published: August 2009

In program debugging, fault localization identifies the exact locations of program faults. Finding these faults using an ad-hoc approach or based only on programmers' intuitive guesswork can be very time consuming. A better way is to use a well-justified method, supported by case studies for its effectiveness, to automatically identify and prioritize suspicious code for an examination of possible fault locations. To do so, we propose the use of a back-propagation (BP) neural network, a machine learning model which has been successfully applied to software risk analysis, cost prediction, and reliability estimation, to help programmers effectively locate program faults. A BP neural network is suitable for learning the input-output relationship from a set of data, such as the inputs and the corresponding outputs of a program. We first train a BP neural network with the coverage data (statement coverage in our case) and the execution result (success or failure) collected from executing a program, and then we use the trained network to compute the suspiciousness of each executable statement, in terms of its likelihood of containing faults. Suspicious code is ranked in descending order based on its suspiciousness. Programmers will examine such code from the top of the rank to identify faults. Four case studies on different programs (the Siemens suite, the Unix suite, grep and gzip) are conducted. Our results suggest that a BP neural network-based fault localization method is effective in locating program faults.
CONSTRUCTION OF EISENSTEIN SERIES FOR Γ0(p)
Authors: COOPER SHAUN
Published: August 2009

A simple construction of Eisenstein series for the congruence subgroup Γ0(p) is given. The construction makes use of the Jacobi triple product identity and Gauss sums, but does not use the modular transformation for the Dedekind eta-function. All positive integral weights are handled in the same way, and the conditionally convergent cases of weights 1 and 2 present no extra difficulty.
ON THE MAPS FROM X(4p) TO X(4)
Authors: JAAFAR SAMAR , KHURI-MAKDISI KAMAL
Published: August 2009

We study pullbacks of modular forms of weight 1 from the modular curve X(4) to the modular curve X(4p), where p is an odd prime. We find the extent to which such modular forms separate points on X(4p). Our main result is that these modular forms give rise to a morphism F from the quotient of X(4p) by a certain involution ι to projective space, such that F is a projective embedding of X(4p)/ι away from the cusps. We also report on computer calculations regarding products of such modular forms, going up to weight 4 for p ≤ 13, and up to weight 3 for p ≤ 23, and make a conjecture about these products and the nature of the singularities at the cusps of the image F(X(4p)/ι).
ON WEIL NUMBERS IN CYCLOTOMIC FIELDS
Authors: ANGLÈS BRUNO , BELIAEVA TATIANA
Published: August 2009

In this paper, we study the p-adic behavior of Weil numbers in the cyclotomic ℤp-extension of the pth cyclotomic field. We determine the characteristic ideal of the quotient of semi-local units by Weil numbers in terms of the characteristic ideals of some classical modules that appear in the Iwasawa theory. In a recent preprint [9] by Nguyen Quang Do and Nicolas, a generalization of this result to a semi-simple case was obtained.
THE 2-RANKS OF HYPERELLIPTIC CURVES WITH EXTRA AUTOMORPHISMS
Authors: GLASS DARREN
Published: August 2009

This paper examines the relationship between the automorphism group of a hyperelliptic curve defined over an algebraically closed field of characteristic two and the 2-rank of the curve. In particular, we exploit the wild ramification to use the Deuring–Shafarevich formula in order to analyze the ramification of hyperelliptic curves that admit extra automorphisms and use this data to impose restrictions on the genera and 2-ranks of such curves. We also show how some of the techniques and results carry over to the case where our base field is of characteristic p > 2.
Complex Organic Interstellar Molecules
Authors: Herbst Eric , van Dishoeck Ewine F.
Published: August 2009

Of the over 150 different molecular species detected in the interstellar and circumstellar media, approximately 50 contain 6 or more atoms. These molecules, labeled complex by astronomers if not by chemists, all contain the element carbon and so can be called organic. In the interstellar medium, complex molecules are detected in the denser sources only. Although, with one exception, complex molecules have only been detected in the gas phase, there is strong evidence that they can be formed in ice mantles on interstellar grains. The nature of the gaseous complex species depends dramatically on the source where they are found: in cold, dense regions they tend to be unsaturated (hydrogen-poor) and exotic, whereas in young stellar objects, they tend to be quite saturated (hydrogen-rich) and terrestrial in nature. Based on both their spectra and chemistry, complex molecules are excellent probes of the physical conditions and history of the sources where they reside. Because they are detected in young stellar objects, complex molecules are expected to be common ingredients for new planetary systems. In this review, we discuss both the observation and chemistry of complex molecules in assorted interstellar regions in the Milky Way.
Magnetic Reconnection in Astrophysical and Laboratory Plasmas
Authors: Zweibel Ellen G. , Yamada Masaaki
Published: August 2009

Magnetic reconnection is a topological rearrangement of magnetic field that converts magnetic energy to plasma energy. Astrophysical flares, from the Earth's magnetosphere to γ-ray bursts and sawtooth crashes in laboratory plasmas, may all be powered by reconnection. Reconnection is essential for dynamos and the large-scale restructuring known as magnetic self-organization. We review reconnection theory and evidence for it. We emphasize recent developments in two-fluid physics, and the experiments, observations, and simulations that verify two-fluid effects. We discuss novel environments such as line-tied, relativistic, and partially ionized plasmas, focusing on mechanisms that make reconnection fast, as observed. Because there is evidence that fast reconnection in astrophysics requires small-scale structure, we briefly introduce how such structure might develop. Several areas merit attention for astrophysical applications: development of a kinetic model of reconnection to enable spectroscopic predictions, better understanding of the interplay between local and global scales, the role of collisionless reconnection in large systems, and the effects of flows, including turbulence.
Progenitors of Core-Collapse Supernovae
Authors: Smartt Stephen J.
Published: August 2009

Knowledge of the progenitors of core-collapse supernovae is a fundamental component in understanding the explosions. The recent progress in finding such stars is reviewed. The minimum initial mass that can produce a supernova (SN) has converged to 8 ± 1 M⊙from direct detections of red supergiant progenitors of II-P SNe and the most massive white dwarf progenitors, although this value is model dependent. It appears that most type Ibc SNe arise from moderate mass interacting binaries. The highly energetic, broad-lined Ic SNe are likely produced by massive, Wolf-Rayet progenitors. There is some evidence to suggest that the majority of massive stars above ∼20 M⊙may collapse quietly to black holes and that the explosions remain undetected. The recent discovery of a class of ultrabright type II SNe and the direct detection of some progenitor stars bearing luminous blue variable characteristics suggest some very massive stars do produce highly energetic explosions. The physical mechanism is under debate, and these SNe pose a challenge to stellar evolutionary theory.
Teraelectronvolt Astronomy
Authors: Hinton J.A. , Hofmann W.
Published: August 2009

Ground-based γ-ray astronomy, which provides access to the TeV energy range, is a young and rapidly developing discipline. Recent discoveries in this waveband have important consequences for a wide range of topics in astrophysics and astroparticle physics. This article is an attempt to review the experimental status of this field and to provide the basic formulae and concepts required to begin the interpretation of TeV observations.
The HiDistribution of the Milky Way
Authors: Kalberla Peter M.W. , Kerp Jürgen
Published: August 2009

Neutral atomic hydrogen (Hi) traces the interstellar medium (ISM) over a broad range of physical conditions. Its 21-cm emission line is a key probe of the structure and dynamics of the Milky Way Galaxy. About 50 years after the first detection of the 21-cm line the exploration of the Hi distribution of the Milky Way has undergone a true renaissance. This was triggered by several large-scale 21-cm surveys that became available within the past decade. New all-sky surveys unravel the shape and volume density distribution of the gaseous disk up to its borders. High-resolution Galactic plane surveys disclose a wealth of shells, filaments, and spurs that bear witness to the recycling of matter between stars and the ISM. All these observational results indicate that the Hi gas traces a dynamical Galactic ISM with structures on all scales, from tens of astronomical units to kiloparsecs. The Galaxy can be considered to be a violent, breathing disk surrounded by highly turbulent extra-planar gas.
Hearing Loss: Mechanisms Revealed by Genetics and Cell Biology
Authors: Dror Amiel A. , Avraham Karen B.
Published: August 2009

Hearing loss (HL), or deafness in its most severe form, affects an estimated 28 and 22.5 million Americans and Europeans, respectively. The numbers are higher in regions such as India and the Middle East, where consanguinity contributes to larger numbers of recessively inherited hearing impairment (HI). As a result of work-related difficulties, educational and developmental delays, and social stigmas and exclusion, the economic impact of HL is very high. At the other end of the spectrum, a rich deaf culture, particularly for individuals whose parents and even grandparents were deaf, is a social movement that believes that deafness is a difference in human experience rather than a disability. This review attempts to cover the remarkable progress made in the field of the genetics of HL over the past 20 years. Mutations in a significant number of genes have been discovered over the years that contribute to clinically heterogeneous forms of HL, enabling genetic counseling and prediction of progression of HL. Cell biological assays, protein localization in the inner ear, and detailed analysis of spontaneous and transgenic mouse models have provided an incredibly rich resource for elucidating mechanisms of hereditary hearing loss (HHL). This knowledge is providing answers for the families with HL, who contribute a great deal to the research being performed worldwide.
The Chemical Composition of the Sun
Authors: Asplund Martin , Grevesse Nicolas , Sauval A. Jacques , Scott Pat
Published: August 2009

The solar chemical composition is an important ingredient in our understanding of the formation, structure, and evolution of both the Sun and our Solar System. Furthermore, it is an essential reference standard against which the elemental contents of other astronomical objects are compared. In this review, we evaluate the current understanding of the solar photospheric composition. In particular, we present a redetermination of the abundances of nearly all available elements, using a realistic new three-dimensional (3D), time-dependent hydrodynamical model of the solar atmosphere. We have carefully considered the atomic input data and selection of spectral lines, and accounted for departures from local thermodynamic equilibrium (LTE) whenever possible. The end result is a comprehensive and homogeneous compilation of the solar elemental abundances. Particularly noteworthy findings are significantly lower abundances of C, N, O, and Ne compared to the widely used values of a decade ago. The new solar chemical composition is supported by a high degree of internal consistency between available abundance indicators, and by agreement with values obtained in the Solar Neighborhood and from the most pristine meteorites. There is, however, a stark conflict with standard models of the solar interior according to helioseismology, a discrepancy that has yet to find a satisfactory resolution.
Progesterone stimulates mitochondrial activity with subsequent inhibition of apoptosis in MCF-10A benign breast epithelial cells
Authors: Behera Millie A. , Dai Qunsheng , Garde Rachana , Saner Carrie , Jungheim Emily , Price Thomas M.
Published: August 2009

The effects of progesterone on breast epithelial cells remain poorly defined with observations showing both proliferative and antiproliferative effects. As an example, progesterone levels correlate with increased epithelial cell proliferation, but there is discordance between the dividing cells and the cells with nuclear progesterone receptor expression. The release of paracrine growth factors from nuclear receptor-positive cells has been postulated as a mechanism, since in vitro studies show a lack of growth effect by progesterone in breast epithelial cells lacking nuclear receptors. This study examined possible nongenomic effects of progesterone in breast epithelia by using MCF-10A cells known to lack nuclear progesterone receptor expression. Treatment for 30–60 min with progesterone or the progestin, R5020, increased mitochondrial activity as shown by an increase in mitochondrial membrane potential (hyperpolarization) with a concordant increase in total cellular ATP. The reaction was inhibited by a specific progesterone receptor antagonist and not affected by the translation inhibitor cycloheximide. Progestin treatment inhibited apoptosis induced by activation of the FasL pathway, as shown by a decrease in sub-G1 cell fraction during fluorescence-activated cell sorting and a decrease in caspase 3/7 levels. Progestin treatment did not alter the cell cycle over 48 h. Our study demonstrates a nongenomic action of progesterone on benign breast epithelial cells, resulting in enhanced cellular respiration and protection from apoptosis.
Benefits of oat β-glucan and sucrose feedings on infection and macrophage antiviral resistance following exercise stress
Authors: Murphy E. Angela , Davis J. Mark , Carmichael Martin D. , Mayer Eugene P. , Ghaffar Abdul
Published: August 2009

Oat β-glucan can counteract the exercise-induced increased risk for upper respiratory tract infection (URTI) in mice, which is at least partly mediated by its effects on lung macrophages. Substantial evidence in humans indicates that carbohydrate-containing sports drinks can offset the decreased immune function associated with stressful exercise. However, no studies in animals or humans have directly examined their effects on URTI using a controlled virus-challenge model. We examined the effects of sucrose feedings alone and in combination with oat β-glucan on susceptibility to infection and on macrophage antiviral resistance in mice following stressful exercise. These effects were also examined in rested, nonimmunocompromised control mice. Mice were assigned to one of four groups: H2O (water), sucrose (S), oat β-glucan (OβG), and sucrose + oat β-glucan (S+OβG). OβG and S treatments consisted of a solution of 50% OβG and 6% sucrose, respectively, and were administered in drinking water for 10 consecutive days. Exercise consisted of a treadmill run to fatigue performed on three consecutive days. Mice were then intranasally inoculated with a standardized dose of herpes simplex virus 1 (HSV-1) and monitored for morbidity and mortality for 21 days. Additional mice were used to determine macrophage antiviral resistance. In the exercise experiment, S, OβG, and S+OβG all reduced morbidity ( P < 0.05), while only S+OβG reduced mortality ( P < 0.05). Macrophage antiviral resistance was also increased in S, OβG, and S+OβG treatments ( P < 0.05). In resting controls, S and S+OβG reduced morbidity and mortality ( P < 0.05) and showed a trend toward increased macrophage antiviral resistance. There was no significant additive effect of S and OβG in either control or exercised animals. These data extend our previous work on the benefits of oat β-glucan to show that sucrose feedings have similar effects on susceptibility to respiratory infection and macrophage antiviral resistance in both resting controls and following exercise stress.
Modulation of myocellular fat stores: lipid droplet dynamics in health and disease
Authors: Meex Ruth C. R. , Schrauwen Patrick , Hesselink Matthijs K. C.
Published: August 2009

Storage of fatty acids as triacylglycerol (TAG) occurs in almost all mammalian tissues. Whereas adipose tissue is by far the largest storage site of fatty acids as TAG, subcellular TAG-containing structures—referred to as lipid droplets (LD)—are also present in other tissues. Until recently, LD were considered inert storage sites of energy dense fats. Nowadays, however, LD are increasingly considered dynamic functional organelles involved in many intracellular processes like lipid metabolism, vesicle trafficking, and cell signaling. Next to TAG, LD also contain other neutral lipids such as diacylglycerol. Furthermore, LD are coated by a monolayer of phospholipids decorated with a variety of proteins regulating the delicate balance between LD synthesis, growth, and degradation. Disturbances in LD-coating proteins may result in disequilibrium of TAG synthesis and degradation, giving rise to insulin-desensitizing lipid intermediates, especially in insulin-responsive tissues like skeletal muscle. For a proper and detailed understanding, more information on processes and players involved in LD synthesis and degradation is necessary. This, however, is hampered by the fact that research on LD dynamics in (human) muscle is still in its infancy. A rapidly expanding body of knowledge on LD dynamics originates from studies in other tissues and other species. Here, we aim to review the involvement of LD-coating proteins in LD formation and degradation (LD dynamics) and to extrapolate this knowledge to human skeletal muscle and to explore the role of LD dynamics in myocellular insulin sensitivity.
Reduction of renal triglyceride accumulation: effects on proximal tubule Na+/H+exchange and urinary acidification
Authors: Bobulescu I. Alexandru , Dubree Michele , Zhang Jianning , McLeroy Paul , Moe Orson W.
Published: August 2009

One main pathophysiological mechanism underlying the increased risk for uric acid nephrolithiasis in humans with the metabolic syndrome is the excretion of unduly acidic urine, in part because of reduced excretion of the main urinary buffer, ammonium. The Zucker diabetic fatty (ZDF) rat, an established rodent model of the metabolic syndrome, has similar urinary abnormalities, attributed in part to lower expression and activity of the principal mediator of proximal tubule ammonium excretion, brush-border membrane Na+/H+exchanger 3 (NHE3). These defects are associated with renal tubular steatosis in ZDF rats, but the causal relationship between renal steatosis and defective urinary acidification has not been investigated in vivo. We hypothesized that reduction of renal steatosis would commensurately normalize urinary acidification parameters. We treated ZDF rats with thiazolidinediones to reduce nonadipose tissue steatosis. Four weeks of treatment reduced renal triglyceride accumulation and restored urinary acidification parameters in ZDF rats to levels comparable to their lean littermates; urinary acidification was not affected by treatment in lean rats. To further document the direct effects of fat, we showed that functional abnormalities induced by fat loading in a cell culture model of proximal tubule steatosis and lipotoxicity can be reversed by fat removal but not by thiazolidinediones alone. Together, these findings support the causative role of renal steatosis in the pathogenesis of urinary acidification defects, demonstrate reversibility upon lipid removal, and highlight a potential therapeutic strategy for renal abnormalities in the metabolic syndrome.
Short-term pressure induced suppression of the short-latency response: a new methodology for investigating stretch reflexes
Authors: Leukel Christian , Lundbye-Jensen Jesper , Gruber Markus , Zuur Abraham T. , Gollhofer Albert , Taube Wolfgang
Published: August 2009

During experiments involving ischemic nerve block, we noticed that the short-latency response (SLR) of evoked stretches in m. soleus decreased immediately following inflation of a pneumatic cuff surrounding the lower leg. The present study aimed to investigate this short-term effect of pressure application in more detail. Fifty-eight healthy subjects were divided into seven protocols. Unilateral stretches were applied to the calf muscles to elicit a SLR, and bilateral stretches to evoke a subsequent medium-latency response (MLR). Furthermore, H-reflexes and sensory nerve action potentials (SNAPs) were recorded. Additionally, stretches were applied with different velocities and amplitudes. Finally, the SLR was investigated during hopping and in two protocols that modified the ability of the muscle-tendon complex distal to the cuff to stretch. All measurements were performed with deflated and inflated cuff. Results of the protocols were as follows: 1) inflation of the cuff reduced the SLR but not the MLR; 2) the H-reflex, the M-wave, and, 3) SNAPs of n. tibialis remained unchanged with deflated and inflated cuff; 4) the SLR was dependent on the stretch velocity with deflated and also inflated cuff; 5 and 6) the reduction of the SLR by the cuff was dependent on the elastic properties of the muscle-tendon complex distal to the cuff; and 7) the cuff reduced the SLR during hopping. The present results suggest that the cuff did not affect the reflex arc per se. It is proposed that inflation restricted stretch of the muscles underlying the cuff so that most of the length change occurred in the muscle-tendon complex distal to the cuff. As a consequence, the muscle spindles lying within the muscle may be less excited, resulting in a reduced SLR. Due to its applicability in functional tasks, the introduced method can be a useful tool to study afferent feedback in motor control.
Dependence of the Roll Angular Vestibuloocular Reflex (aVOR) on Gravity
Authors: Yakushin Sergei B. , Xiang Yongqing , Cohen Bernard , Raphan Theodore
Published: August 2009

Little is known about the dependence of the roll angular vestibuloocular reflex (aVOR) on gravity or its gravity-dependent adaptive properties. To study gravity-dependent characteristics of the roll aVOR, monkeys were oscillated about a naso-occipital axis in darkness while upright or tilted. Roll aVOR gains were largest in the upright position and decreased by 7–15% as animals were tilted from the upright. Thus the unadapted roll aVOR gain has substantial gravitational dependence. Roll gains were also decreased or increased by 0.25 Hz, in- or out-of-phase rotation of the head and the visual surround while animals were prone, supine, upright, or in side-down positions. Gain changes, determined as a function of head tilt, were fit with a sinusoid; the amplitudes represented the amount of the gravity-dependent gain change, and the bias, the gravity-independent gain change. Gravity-dependent gain changes were absent or substantially smaller in roll (≈5%) than in yaw (25%) or pitch (17%), whereas gravity-independent gain changes were similar for roll, pitch, and yaw (≈20%). Thus the high-frequency roll aVOR gain has an inherent dependence on head orientation re gravity in the unadapted state, which is different from the yaw/pitch aVORs. This inherent gravitational dependence may explain why the adaptive circuits are not active when the head is tilted re gravity during roll aVOR adaptation. These behavioral differences support the idea that there is a fundamental difference in the central organization of canal-otolith convergence of the roll and yaw/pitch aVORs.