bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of Hb E mutation (β26, GAG‐AAG, Glu‐Lys) using allelic discrimination analysis
Authors: SANGKITPORN S. , SANGKITPORN S. K. , SANGNOI A. , DUANGRUANG S.
Published: January 2009

A method for detection of hemoglobin (Hb) E mutation was developed based on allelic discrimination analysis. Two probes labeled with different fluorescent reporter dyes were designed to specifically detect variation of a single nucleic acid polymorphism (SNP) site in the target template sequence. Polymerase chain reaction (PCR) products of normal allele and mutant allele were detected directly by analyzing fluorescent signal of each probe. This method was validated in term of accuracy (by comparing with sequence analysis) and reproducibility. The % CV between run precision was 5.16–8.86%. The narrow scatter of the results confirmed the reproducibility of the assay. This technique is a rapid, reliable and cost‐effective method to differentiate Hb E homozygosity from β0‐thalassemia/Hb E in populations with a high frequency of β‐thalassemia and Hb E.
Methylation of DAPK1 promoter: frequent but not an adverse prognostic factor in myelodysplastic syndrome
Authors: QIAN J. , YAO D.‐M. , LIN J. , WANG Y.‐L. , HAN L.‐X. , XU W.‐R. , WU C.‐Y.
Published: January 2009

Promoter hypermethylation plays an important role in the inactivation of cancer‐related genes. This abnormality occurs early in leukemogenesis and seems to be associated with poor prognosis in myelodsplastic syndrome (MDS). The identification of more inactivated tumor suppressor genes contributing to the development of MDS may lead to further elucidation of the biology of this disease and help to identify novel targets for therapy. In this study, the methylation status of death‐associated protein kinase 1 (DAPK1) gene promoter was analyzed by using methylation‐specific polymerase chain reaction in bone marrow (BM) samples from 59 patients with different stages of MDS. The abnormal methylation of the DAPK1 gene was found in 37 of 59 (62.7%) MDS cases. The correlation was significant between the sex and the methylation status of DAPK1 promoter in MDS patients (R = 0.332, P = 0.010). Furthermore, methylation status of DAPK1 promoter was associated with the percentage of BM blasts (R = 0.346, P = 0.010) and International Prognosis Scoring System (IPSS) groups (R = 0.278, P = 0.034). The estimated 50% survival time of the methylated DAPK1 group and unmethylated group was 20 and 33 months, respectively. There was no significant difference between these two groups (χ2 = 0.652, P = 0.419). Multivariate analysis identified the age older than 50 years, the Int‐2/high‐risk categories of IPSS and the advanced stage MDS (RAEB‐1/RAEB‐2) in WHO classification as negative prognostic factors (P < 0.05). Aberrant methylation of DAPK1 gene promoter had no influence on the prognosis of MDS despite of its increasing occurrence during disease progression.
Acute variation of leucocytes counts following a half‐marathon run
Authors: LIPPI G. , BANFI G. , MONTAGNANA M. , SALVAGNO G. L. , SCHENA F. , GUIDI GIAN CESARE
Published: January 2009

There is growing interest on haematological changes following elite and recreation sports. However, no information is available on leucocyte variations after an intermediate‐distance run. Complete blood cell count was assessed on 17 trained, middle‐aged males before a 21‐km half‐marathon, at the end and 3, 6, 24 h thereafter. Statistically significant variations by one‐way analysis of variance were observed for all the parameters tested. Haematocrit, haemoglobin and red blood cells and platelet count increased significantly by the end of the run and returned to pre‐run values 3 h thereafter. White blood cells, neutrophils, monocytes and basophils counts increased after the run, reached the peak at 3 h and returned to the baseline after 24 h. Conversely, the eosinophils count significantly decreased after the run, reached a nadir at 3 h and slowly returned to pre‐run values at 24 h. The lymphocytes count significantly increased after the run, decreased 3 h thereafter and returned to pre‐run values after 6 h. These results show that an intermediate‐distance run, which is a popular form of recreational sports worldwide, is associated with transitory leucocytosis, neutrophilia, monocytosis and basophilia, but it also induces acute eosinopenia, all changes being completely reversed 24 h thereafter.
Increased incidence of saprophytic bacteria, coliforms and E. coli following severe flooding requires risk assessment for human health: results of the River Elbe flood in August 2002
Authors: Karrasch B. , Mehrens M. , Link U.
Published: January 2009

In August 2002, flooding in the Elbe valley caused severe damage of sewage treatment plants and networks. We investigated the impact of flooding on the bacteriological water quality (colony‐forming units of saprophytic bacteria, coliform bacteria and Escherichia coli) compared with levels from previous and subsequent years. The flood introduced organic matter and elevated saprophytic bacteria levels, and a general increase of coliform bacteria. Markedly high loads of coliforms and E. coli were detected in the water column in areas where damage to sewage treatment plants was rife, exceeding the European Commission's Bathing Water Directive. The rapid disappearance from the water column may partly be caused by sedimentation creating deposits on pasture, farmland and in built‐up areas, which could represent a health hazard. Future flood risk reduction should therefore be focused on the protection of sewage systems and hygienic monitoring of floodwater and flood sediments.
Comparative analysis of statistical and catchment modelling approaches to river flood frequency estimation
Authors: Calver A. , Stewart E. , Goodsell G.
Published: January 2009

The paper compares results from two approaches to the quantification of river flood frequencies applicable nationally in Britain. One approach uses both the flood peak and event‐based methods of the Flood Estimation Handbook (FEH) of current water industry practice and the other approach is a recently developed set of continuous simulation techniques using parameter‐sparse modelling of catchment flood runoff response. The methods were applied to over a hundred sites in Britain, treated as if without flow data, although such observations existed and were used only for testing purposes. Errors of ≤20% in peak flows at ungauged sites are currently very good in this hydrologically challenging context; errors of up to around 35% may have to be contended with in flood management practice. The results from the FEH statistical method reinforce its established role in peak‐flow estimation. On the basis of the aspects that have been tested here, the emerging continuous simulation approaches show considerable potential to offer good performance for peaks and flow time series. The errors associated with the FEH unit hydrograph approach reflect the additional challenge it incorporates of ungauged rainfall estimation in addition to ungauged discharge.
Mapping Hurricane Rita inland storm tide
Authors: Berenbrock C. , Mason, Jr. R.R. , Blanchard S.F.
Published: January 2009

Flood‐inundation data are most useful for decision makers when presented in the context of maps of affected communities and (or) areas. But because the data are scarce and rarely cover the full extent of the flooding, interpolation and extrapolation of the information are needed. Many geographic information systems provide various interpolation tools, but these tools often ignore the effects of the topographic and hydraulic features that influence flooding. A barrier mapping method was developed to improve maps of storm tide produced by Hurricane Rita. Maps were developed for the maximum storm tide and at 3‐h intervals from midnight (00:00 hours) through noon (12:00 hours) on 24 September 2005. The improved maps depict storm‐tide elevations and the extent of flooding. The extent of storm‐tide inundation from the improved maximum storm‐tide map was compared with the extent of flood inundation from a map prepared by the Federal Emergency Management Agency (FEMA). The boundaries from these two maps generally compared quite well especially along the Calcasieu River. Also a cross‐section profile that parallels the Louisiana coast was developed from the maximum storm‐tide map and included FEMA high‐water marks.
Modeling the magnetic pickup of an electric guitar
Authors: Horton Nicholas G. , Moore Thomas R.
Published: January 2009

The magnetic pickup of an electric guitar uses electromagnetic induction to convert the motion of a ferromagnetic guitar string to an electrical signal. Although the magnetic pickup is often cited as an everyday application of Faraday’s law, few sources mention the distortion that the pickup generates when converting the motion of a string to an electric signal, and fewer analyze and explain this distortion. We model the magnet and ferromagnetic wire as surfaces with magnetic charge and construct an intuitive model that accurately predicts the output of a magnetic guitar pickup. This model can be understood by undergraduate students and provides an excellent learning tool due to its straightforward mathematics and intuitive algorithm. Experiments show that it predicts the change in a magnetic field due to the presence of a ferromagnetic wire with a high degree of accuracy.
Splitting the wavefunctions of two particles in two boxes
Authors: van Enk S. J.
Published: January 2009

I consider two identical quantum particles in two boxes. We can split each box and thereby the wavefunction of each particle into two parts. When two half boxes are interchanged and combined with the other halves, where are the two particles? I solve this problem for two identical bosons and for two identical fermions. The solution can be used to define a measurement that yields some information about the relative phase between the two parts of a split wavefunction.
A simple function for the description of near-exponential decays: The stretched or compressed hyperbola
Authors: Whitehead Lorne , Whitehead Ryan , Valeur Bernard , Berberan-Santos Mario
Published: January 2009

The modeling of systems that exhibit near-exponential decay is most commonly done using a sum of exponentials or a stretched exponential. We note some drawbacks of these representations and present an alternative model, the stretched or compressed hyperbola, first described by E. Becquerel in the 1860s. This representation might be more helpful for interpolation, extrapolation, and classification of decays and requires only one additional parameter compared to simple exponential decay.
The 1925 Born and Jordan paper “On quantum mechanics”
Authors: Fedak William A. , Prentis Jeffrey J.
Published: January 2009

The 1925 paper “On quantum mechanics” by M. Born and P. Jordan, and the sequel “On quantum mechanics II” by M. Born, W. Heisenberg, and P. Jordan, developed Heisenberg’s pioneering theory into the first complete formulation of quantum mechanics. The Born and Jordan paper is the subject of the present article. This paper introduced matrices to physicists. We discuss the original postulates of quantum mechanics, present the two-part discovery of the law of commutation, and clarify the origin of Heisenberg’s equation. We show how the 1925 proof of energy conservation and Bohr’s frequency condition served as the gold standard with which to measure the validity of the new quantum mechanics.
How weak is a weak probe in laser spectroscopy?
Authors: Sherlock Ben E. , Hughes Ifan G.
Published: January 2009

Laser spectroscopy experiments are often conducted with a probe that does not significantly alter the medium’s properties. For a two-level atom a clear measure of the strength of a probe beam in terms of the saturation intensity is known. We show that for a multilevel atom the situation is very different, and the effects of optical pumping are crucial to understanding the opacity of the medium. We present a simple theoretical analysis for Doppler-broadened spectroscopy of alkali metals on the D2 line that emphasizes the importance of the transient nature of the population dynamics, and the crucial role of the distribution of the times of flight of atoms through the probe beam. Experimental results are obtained with room temperature rubidium vapor probed by an extended-cavity diode laser and confirm our theoretical prediction.
Oscillator experiments with periods between the simple pendulum and a rigid rod
Authors: Zamora J. C. , Fajardo F. , Rodríguez J.-Alexis
Published: January 2009

Three experiments using a simple multiple pendulum in a gravitational field are presented. The first experiment shows the behavior of the period of the multiple pendulum as a function of its linear mass density. In the second experiment the linear mass density is fixed and the total length of the multiple pendulum is changed. It is shown experimentally that the period of a multiple pendulum lies between the period of a simple pendulum and the period of a rigid rod. The experimental results are compared with a theoretical approach using the Lagrangian formalism and numerical solutions.
Broad-band multispectral microscope for imaging transmission spectroscopy employing an array of light-emitting diodes
Authors: Brydegaard Mikkel , Guan Zuguang , Svanberg Sune
Published: January 2009

Optical spectral analysis and multispectral imaging provide powerful means for characterizing samples in a wide variety of applications and on many spatial scales. We present a simple implementation of these techniques in the context of microscopy. A modified commercial microscope equipped with a CMOS imaging detector, combined with an array of light emitting diodes with emission ranging from ultraviolet to near-infrared wavelengths, is described, and examples of information enhancement using multivariate analysis are presented.
Comparing the efficacy of multimedia modules with traditional textbooks for learning introductory physics content
Authors: Stelzer Timothy , Gladding Gary , Mestre José P. , Brookes David T.
Published: January 2009

We compared the efficacy of multimedia learning modules with traditional textbooks for the first few topics of a calculus-based introductory electricity and magnetism course. Students were randomly assigned to three groups. One group received the multimedia learning module presentations, and the other two received the presentations via written text. All students were then tested on their learning immediately following the presentations as well as 2weeks later. The students receiving the multimedia learning modules performed significantly better on both tests than the students experiencing the text-based presentations.
Electromagnetically induced transparency in rubidium
Authors: Olson Abraham J. , Mayer Shannon K.
Published: January 2009

We investigate ladder-type electromagnetically induced transparency (EIT) in rubidium gas. The theoretical absorption profile of a weak probe laser beam at 780.2nm (5S1∕2→5P3∕2) is modeled in the presence of a strong coupling laser beam at 776.0nm (5P3∕2→5D5∕2) and the absorption transparency window is characterized. We use two grating-feedback diode lasers and observe EIT experimentally in rubidium and compare the results to the theory. This experiment brings quantum optics into the advanced undergraduate laboratory and utilizes equipment and expertise commonly available in laboratories equipped to perform diode-laser-based absorption spectroscopy of rubidium.
Analog of Optical Elements for Sound Waves in Air
Authors: Gluck Paul , Perkalskis Benjamin
Published: January 2009

Optical elements manipulate light waves. They may be used to focus the light or to change the phase, the polarization, the direction, or the intensity of light. Many of these functions are often demonstrated with microwaves, since the devices normally available in teaching laboratories produce wavelengths in the centimeter range and are therefore more tangible. The same can be said for sound waves for frequencies in the kHz range. This property is the clue for producing elements such as half-wave plates, zone plates, and lenses for sound waves, based on techniques that have been developed for microwaves. This is the subject of the present article. Readers might wish to build some of these devices, which would then help to impress on students the unity of wave phenomena.
The Glass Computer
Authors: Paesler M. A.
Published: January 2009

Digital computers use different kinds of memory, each of which is either volatile or nonvolatile. On most computers only the hard drive memory is nonvolatile, i.e., it retains all information stored on it when the power is off. When a computer is turned on, an operating system stored on the hard drive is loaded into the computer's memory cache and system memory. Cache and system memory are volatile, i.e., data in them are lost when the computer is powered down. A more ideal computer would have nonvolatile memory for both cache and system memory to allow for “instant-on” capabilities. Of course any such memory would have to be as fast and as durable as existing volatile devices to be considered an improvement over current systems.
Baking Soda and Vinegar Rockets
Authors: Claycomb James R. , Zachary Christopher , Tran Quoc
Published: January 2009

Rocket experiments demonstrating conservation of momentum will never fail to generate enthusiasm in undergraduate physics laboratories. In this paper, we describe tests on rockets from two vendors1,2 that combine baking soda and vinegar for propulsion. The experiment compared two analytical approximations for the maximum rocket height to the experimentally measured rocket height. Baking soda and vinegar rockets present fewer safety concerns and require a smaller launch area than rapid combustion chemical rockets. Both kits were of nearly identical design, costing ∼$20. The rockets required roughly 30 minutes of assembly time consisting of mostly taping the soft plastic fuselage to the Styrofoam nose cone.
Journey into Problem Solving: A Gift from Polya
Authors: Lederman Eric
Published: January 2009

In How to Solve It, accomplished mathematician and skilled communicator George Polya describes a four-step universal solving technique designed to help students develop mathematical problem-solving skills. By providing a glimpse at the grace with which experts solve problems, Polya provides definable methods that are not exclusive to mathematicians but of interest to cognitive psychologists and problem solvers in all fields. I had the good fortune to be introduced to Polya's ideas in my first undergraduate class in physics.
The Current in a Wire
Authors: Thompson Keith
Published: January 2009

This little problem arose because I was frustrated with the standard electromagnetism texts, which show the magnetic field due to a current-bearing wire outside the wire ∝1/r and inside ∝r. However, they never point out that the moving electrons must be influenced by the magnetic field created by the other moving electrons. Clearly this must affect the solution. In this paper we will determine what that magnetic field does.
An In-Class Discussion Activity on the Nature of Science and Intelligent Design
Authors: Thomas Brian C.
Published: January 2009

In this paper I describe an in-class discussion activity aimed at helping elementary education majors in a physical science course think about issues surrounding the inclusion of “Intelligent Design” in public school science standards. I discuss the background instruction given, the content of the activity, and some results from its use in class.
Dimensional Analysis and General Relativity
Authors: Lovatt Ian
Published: January 2009

Newton's law of gravitation is a central topic in the first-year physics curriculum. A lecturer can go beyond the physical details and use the history of gravitation to discuss the development of scientific ideas; unfortunately, the most recent chapter in this history, general relativity, is not covered in first-year courses. This paper discusses some topics that can be introduced with the judicious use of the dimensionless quantity GM/Rc2: deflection of light by a massive object, perihelion precession, gravitational redshifts, and the Global Positioning System (GPS).
A Circular Motion Activity with Hot Wheels® Rev-Ups
Authors: Wagner Glenn
Published: January 2009

Hot Wheels® Rev-Ups1 provide a pedagogically engaging and inexpensive culminating activity for the application of circular motion with constant speed in introductory mechanics. The introductory Rev-Up, shown in Fig. 1, consists of a very durable car with two strong magnets built into the front and back of the car. The track is a piece of flexible plastic with a built-in metallic strip through its center that can then be formed into a circle. Pushing the car forward several times on a flat surface allows the car to move in a vertical circle when placed inside the track. What makes this toy attractive is that the gearing system allows the car to move at a relatively constant speed for about three to five seconds before slowing down appreciably.
Chemical–environment interactions affecting the risk of impacts on aquatic organisms: A review with a Canadian perspective — interactions affecting exposure
Authors: Couillard Catherine M. , Macdonald Robie W. , Courtenay Simon C. , Palace Vince P.
Published: January 2009

As a consequence of human activity, the variability and range of environmental conditions is increasing. We review how the interactions between toxic chemicals and environmental change may affect exposure of aquatic organisms to stressful conditions and therefore alter the risk of deleterious impacts. Even in the absence of new inputs of contaminants, changing environmental conditions alters the transport, transformation and distribution of contaminants and their bioavailability. Conversely, some toxic chemicals modify the exposure of aquatic species to other stressors by affecting species distribution, behaviour or habitat. Across Canada there are a number of specific examples where interactions between contaminants and environmental change are probably harming aquatic species. In the Arctic, change in foraging brought on by change in ice regime, is a plausible mechanism to explain the marked recent increase in mercury concentrations in Beaufort Sea beluga whales. On the Pacific coast, chemical exposure by itself or in combination with other environmental factors, is a leading suspect for altered migration timing of some salmon stocks in the Fraser River leading to massive pre-spawning mortality. In the North Atlantic, short-term exposure of Atlantic salmon to endocrine-disrupting substances in their freshwater natal environments later leads to detectable effects at the time of their migration to saltwater. In Alberta, biotic and abiotic characteristics of the habitat dramatically affect exposure pathways and the risk of toxic effects of selenium in early life stages of trout. A better understanding of the interactions between toxic chemicals and environmental factors is a fundamental requirement for efficient management and protection of aquatic ecosystems.
Chemical–environment interactions affecting the risk of impacts on aquatic organisms: A review with a Canadian perspective — interactions affecting vulnerability
Authors: Couillard Catherine M. , Courtenay Simon C. , Macdonald Robie W.
Published: January 2009

Environmental change can increase the vulnerability of aquatic species to toxic chemicals by challenging an organism’s aptitude to respond to chemicals or to repair toxic injury or by modifying animal behaviours like migration or predation. On the other hand, xenobiotics may affect the capacity of aquatic species to adapt to environmental challenges that come with change (e.g., pathogens, temperature). Across Canada we have identified a number of circumstances where chemicals and environmental variability have likely worked together to affect vulnerability of aquatic organisms. For example in the Maritimes, exposure to municipal wastewater or bleached kraft pulp mill effluent altered immune function in bivalves and increased their risk of developing haemocytic neoplasia, a disease known to cause high mortality. Northwest Atlantic cod stocks have experienced large-scale changes in environment and exhibit marked seasonal cycles in energy reserves. The risk associated with subsequent redistribution of persistent chemicals in the body together with nutritional deficiency is presently under evaluation since it could affect the recovery of these endangered stocks. In the Great Lakes, the introduction of an invasive fish species, the alewife, modified the diet of salmonids, which led to a deficiency of the vitamin thiamine in eggs causing early mortality. Contaminants may interact with thiamine deficiency and thus critically impair recruitment of salmonids. Viewing the risks presented by toxic chemicals from the point of view of species vulnerability, offers managers opportunities to mitigate such risks, for example, through habitat, ocean and fisheries management. Further research is needed to develop biomarkers of vulnerability, identify most vulnerable life stages and populations, to understand the interactions between global environmental changes, nutritional status, pathogens and toxic chemicals, and to develop integrated approaches to manage vulnerability of aquatic ecosystems to toxic chemicals.
Taxonomic sufficiency: The influence of taxonomic resolution on freshwater bioassessments using benthic macroinvertebrates
Authors: Jones F. Chris
Published: January 2009

Changing the taxonomic scale of a biotic-assemblage dataset influences our ability to detect ecological patterns. In bioassessments, a test-site’s biological community is compared against a benchmark to indicate ecosystem condition, but the taxonomic resolution needed to judge impairment reliably is the subject of much scientific debate. This paper reviews taxonomic sufficiency for freshwater benthic-macroinvertebrate bioassessments. Three main issues are discussed: (1) the ecological significance of different taxonomic aggregations; (2) trade-offs involving taxonomic detail and information content versus money, time, expertise, and data quality; and (3) sampling- and analytical-method-specific factors affecting taxonomic sufficiency. Although Species should be the default taxonomic level for bioassessments, taxonomic sufficiency is chiefly determined by a study’s purpose, and pragmatism often dictates reduced detail. When a taxonomic-minimalism approach is necessary, a quantitative criterion for taxonomic sufficiency should be specified; this criterion should be based on an optimization of cost-benefit trade-offs associated with different taxonomic scales. Mixed-level aggregations, as well as morpho-species and ecological-trait classifications should be considered in this optimization process. Looking to the future, closer ties between taxonomists and bioassessment researchers would benefit both of their disciplines. Such coordination would provide the autoecological information and better diagnostic tools (such as keys and molecular methods) needed for biomonitoring, and better (and more widespread) biomonitoring would fuel taxonomy’s resurgence.
Forest management and soil respiration: Implications for carbon sequestration
Authors: Peng Yuanying , Thomas Sean C. , Tian Dalung
Published: January 2009

It is recognized that human activities, such as fossil fuel burning, land-use change, and forest harvesting at a large scale, have resulted in the increase of greenhouse gases in the atmosphere since the onset of the industrial revolution. The increasing amounts of greenhouse gases, particularly CO2in the atmosphere, is believed to have induced climate change and global warming. With the ability to remove CO2from the atmosphere through photosynthesis, forests play a critical role in the carbon cycle and carbon sequestration at both global and local scales. It is necessary to understand the relationship between forest soil carbon dynamics and carbon sequestration capacity, and the impact of forest management practices on soil CO2efflux for sustainable carbon management in forest ecosystems. This paper reviews a number of current issues related to (1) carbon allocation, (2) soil respiration, and (3) carbon sequestration in the forest ecosystems through forest management strategies. The contribution made by forests and forest management in sequestrating carbon to reduce the CO2concentration level in the atmosphere is now well recognized. The overall carbon cycle, carbon allocation of the above- and belowground compartments of the forests, soil carbon storage and soil respiration in forest ecosystems and impacts of forest management practices on soil respiration are described. The potential influences of forest soils on the buildup of atmospheric carbon are reviewed.
The maintenance of understory residual flora with even-aged forest management: A review of temperate forests in northeastern North America
Authors: Moola F.M. , Vasseur L.
Published: January 2009

This study reviews the effects of even-aged forest management (primarily clearcut logging) on the dynamics, structure, and composition of understory vascular plant communities in remnant late-successional (old-growth and old re-growth) forests of northeastern North America. Less than 1% of forested land in the region has never been cleared and remnant patches of primary woodland (i.e., continuously forested since European colonization; ~350 BP) are few, small and isolated within a second-growth landscape that is increasingly managed in open and immature forest age-classes. The historical loss and fragmentation of pre-settlement forested habitat has generated considerable scientific and public debate about whether additional declines in late-successional woodland, as a result of contemporary land uses (e.g., clearcut logging), threaten species that are associated with old forest conditions. We focused particular attention on residual plants (i.e., flora associated with late-successional forests) that may be dependent upon older stand conditions for maximal growth or that are less common within intensively managed landscapes. Despite a general community-wide resiliency to clearcutting, we found that a number of residual plants in northeastern forests are typically eliminated or have a reduced presence in recovering stands after logging (e.g., Oxalis montana (L.), Aralia nudicaulis (L.), Taxus candensis (Marsh.)). The most sensitive species to clearcutting include mycotrophs, taxa with limited seed dispersal and (or) low rates of clonal expansion (<10 cm/year), and species reliant on specific seedbed conditions associated with older forests (e.g., decayed logs). These results suggest that the preservation of remnant late-successional forests (both old-growth and old re-growth) may be necessary for the maintenance of some residual plant populations in highly disturbed and fragmented forest landscapes in the northeastern North America.
Logging impacts on the biogeochemistry of boreal forest soils and nutrient export to aquatic systems: A review
Authors: Kreutzweiser David P. , Hazlett Paul W. , Gunn John M.
Published: January 2009

Logging disturbances in boreal forest watersheds can alter biogeochemical processes in soils by changing forest composition, plant uptake rates, soil conditions, moisture and temperature regimes, soil microbial activity, and water fluxes. In general, these changes have often led to short-term increases in soil nutrient availability followed by increased mobility and losses by leaching to receiving waters. Among the studies we reviewed, dissolved organic carbon (DOC) exports usually increased after logging, and nitrogen (N) mineralization and nitrification often increased with resulting increased N availability and exports to receiving waters. Similar processes and responses occurred for phosphorus (P), but to a lesser extent than for N. In most cases, base cations were released and exported to receiving waters after logging. Several studies demonstrated that stem-only or partial-harvest logging reduced the impacts on nutrient release and exports in comparison to whole-tree clear-cutting. Despite these logging-induced increases in soil nutrient availability and movement to receiving waters, most studies reported little or no change in soil chemical properties. However, responses to logging were highly variable and often site specific. The likelihood, extent and magnitude of logging impacts on soil nutrient cycling and exports in boreal forest watersheds will be dependent on soil types, stand and site conditions, hydrological connectivity, post-logging weather patterns, and type and timing of harvest activities. Additionally, logging impacts can interact with, and be confounded by, atmospheric pollutant deposition and climate change. Further watershed-level empirical studies and modeling efforts are required to elucidate these interactions, to improve predictive capabilities, and to advance forest management guidelines for sustaining forest soil productivity and limiting nutrient exports.
IS COSMOLOGICAL ACCELERATION DRIVEN BY CLASSICAL SPACE–TIME GEOMETRY?
Authors: BLUDMAN SIDNEY
Published: January 2009

The homogeneous expansion history H(z) of our universe (Hubble diagram) measures only kinematic variables, it cannot fix the underlying dynamics driving the recent acceleration: cosmographic measurements of the homogeneous universe are consistent with either a static fine-tuned cosmological constant or a dynamic "dark energy" mechanism, which itself may be either material dark energy or low-curvature modifications of Einstein gravity (dark gravity). This dark energy/dark gravity degeneracy in the homogeneous expansion observations can only be resolved by observing the growth of the cosmological fluctuations. However, because the "dark energy" evolution is now quasi-static at most, any dynamical effects on the fluctuation growth function g(z) will be minimal. Projected observations may potentially distinguish static from dynamic "dark energy", but distinguishing dynamic dark energy from dark gravity will require a weak lensing shear survey more ambitious than any now projected. Dark gravity is also, in principle, observable in the solar system or in isolated galaxy clusters.

The cosmological constant problem — that quantum material vacuum fluctuations apparently do not gravitate — suggests identifying gravitational "vacuum energy" with classical intrinsic space–time curvature, divorcing it from any quantum material property. This empty space–time curvature appears cosmologically and about isolated sources and can only be fine-tuned, at present. The cosmological coincidence problem — that we live when the ordinary matter density approximates the "gravitational vacuum energy" — on the other hand, is a material problem, calling for an understanding of the observers' role in cosmology. A particularly restrictive weak anthropic principle, that dark energy and dark gravity be indistinguishable, selects static "dark energy" (ΛCDM) and rejects any dynamical effects in the growth of fluctuations.
HOLOGRAPHIC MODIFIED GRAVITY
Authors: SETARE M. R.
Published: January 2009

In this paper, we investigate cosmological application of holographic dark energy density in the modified gravity framework. We employ the holographic model of dark energy to obtain the equation of state for the holographic energy density in a spatially flat universe. Our calculation shows that, taking ΩΛ = 0.73 for the present time, it is possible to have wΛ crossing -1. This implies that one can generate a phantom-like equation of state from a holographic dark energy model in flat universe in the modified gravity cosmology framework. Also, we develop a reconstruction scheme for the modified gravity with f(R) action.
DUALITY INVARIANCE AND COSMOLOGICAL DYNAMICS
Authors: CHIMENTO LUIS P. , ZIMDAHL WINFRIED
Published: January 2009

A duality transformation that interrelates expanding and contracting cosmological models is shown to single out a duality invariant, interacting two-component description of any irrotational, geodesic and shear-free cosmic medium with vanishing three-curvature scalar. We have applied this feature to a system of matter and radiation, to a mixture of dark matter and dark energy, to minimal and conformal scalar fields, and to an enlarged Chaplygin gas model of the cosmic substratum. We have extended the concept of duality transformations to cosmological perturbations and demonstrated the invariance of adiabatic pressure perturbations under these transformations.
DOES THE COSMOLOGICAL TERM INFLUENCE GRAVITATIONAL LENSING?
Authors: KHRIPLOVICH I. B. , POMERANSKY A. A.
Published: January 2009

In this paper, we analyze the bending of light by galaxies or clusters of galaxies in the presence of the Λ term. Using Friedmann–Robertson–Walker (FRW) coordinates, which are used for the description of actual observations, we demonstrate that the cosmological constant does not practically influence the lensing effect.
CASIMIR EFFECT FOR A SPHERICAL SHELL IN DE SITTER SPACE–TIME WITH SIGNATURE CHANGE
Authors: SETARE M. R. , DARABI F.
Published: January 2009

We calculate the Casimir stress on a spherical shell in a de Sitter background corresponding to different metric signatures and cosmological constants, for massless scalar fields that satisfy Dirichlet boundary conditions on the shell. We show that a contribution appears due to signature change, which leads to late-time expansion of the bubbles in this background.
ON THE GENERALIZED CHAPLYGIN GAS: WORSE THAN A BIG RIP OR QUIETER THAN A SUDDEN SINGULARITY?
Authors: BOUHMADI-LÓPEZ MARIAM , GONZÁLEZ-DÍAZ PEDRO F. , MARTÍN-MORUNO PRADO
Published: January 2009

Although it has been believed that models with generalized Chaplygin gas (GCG) do not contain singularities, in previous work we have studied how a big freeze could take place in some kinds of phantom-generalized Chaplygin gas. In the present work, we study some types of generalized Chaplygin gas in order to show how different sorts of singularities could appear in such models, either in the future or in the past. We point out that (i) singularities may not originate from the phantom nature of the fluid, and (ii) if initially the tension of the brane in a brane-world Chaplygin model is large enough, then an infrared cutoff appears in the past.
THE EQUILIBRIUM STRUCTURE OF CHARGED ROTATING RELATIVISTIC STARS
Authors: MIRZA BABUR M.
Published: January 2009

General relativistic equilibrium conditions imply that an electrically charged compact star, in a spherically symmetric configuration, can sustain a huge amount of electric charge (up to 1020 C). The equilibrium, however, is reached under very critical conditions such that a perturbation to the stellar structure can cause these systems to collapse. We study the effects of rotation in charged compact stars and obtain conditions, the modified Tolman–Oppenheimer–Volkoff (TOV) equations, under which such stars form a stable gravitational system against Coulomb repulsion. We assume the star to be rotating slowly. We also assume that the charge density is proportional to the mass density everywhere inside the star. The modified TOV equations for hydrostatic equilibrium are integrated numerically for the general equation of state for a polytrope. The detailed numerical study shows that the centrifugal force adds to the Coulomb pressure in the star. In the stable equilibrium configurations, therefore, a loss in stellar mass (energy) density occurs for higher values of the angular frequency. The additional energy is radiated in the form of electrical energy. The stellar radius is also decreased so that the star does not necessarily becomes more compact.
TACHYON FIELD-INSPIRED DARK ENERGY AND SUPERNOVAE CONSTRAINTS
Authors: REN JIE , MENG XIN-HE
Published: January 2009

The tachyon field in cosmology is studied in this paper by applying the generating function method to obtain exact solutions. The equation of state parameter of the tachyon field is [Formula: see text], which can be expressed as a function in terms of the redshift z. Based on these solutions, we propose some tachyon-inspired dark energy models to explore the properties of the corresponding cosmological evolution. The explicit relations between the Hubble parameter and redshift enable us to test the models with SNe Ia data sets easily. In this paper, we employ the SNe Ia data with the parameter [Formula: see text] measured from the SDSS and the shift parameter [Formula: see text] from WMAP observations to constrain the parameters in our models.
MAGNETOSPHERIC PARTICLE ACCELERATION AND X-RAY EMISSION OF PULSARS
Authors: TAGIEVA SEVINÇ O. , ANKAY AKIN , ANKAY ARZU MERT
Published: January 2009

In this paper, we analyze the available data on isolated X-ray pulsars, their wind nebulae, and the supernova remnants that are connected to some of these sources. It is shown that the electric fields of neutron stars tear off charged particles from the surface of the neutron star and trigger the acceleration of particles. The charged particles are accelerated mainly in the field of a magneto-dipole radiation wave. The power and energy spectra of the charged particles depend on the strength of the magneto-dipole radiation. Therefore, the X-ray radiation is strongly dependent on the rate of rotational energy loss and weakly dependent on the electric field intensity. Coulombic interaction between the charged particles is the main factor for the energy loss and the X-ray spectra of the charged particles.
PHANTOM FIELDS: BOUNCE SOLUTIONS IN THE EARLY UNIVERSE AND S-BRANES
Authors: DZHUNUSHALIEV VLADIMIR , FOLOMEEV VLADIMIR , MYRZAKULOV KAIRAT , MYRZAKULOV RATBAY
Published: January 2009

A cosmological model with two phantom scalar fields with a special choice of the field potential is considered. The obtained regular solution describes a bounce with a subsequent transition to the de Sitter stage of the expansion of the universe. This solution could also be interpreted as an S-brane solution.
(‐)‐Epigallocatechin Gallate Reduces Platelet‐Derived Growth Factor‐BB‐Stimulated Interleukin‐6 Synthesis in Osteoblasts: Suppression of SAPK/JNK
Authors: Takai Shinji , Matsushima-Nishiwaki Rie , Adachi Seiji , Natsume Hideo , Minamitani Chiho , Mizutani Jun , Otsuka Takanobu , Tokuda Haruhiko , Kozawa Osamu
Published: January 2009

We previously showed that the mitogen‐activated protein (MAP) kinase superfamily, p44/p42 MAP kinase, p38 MAP kinase, and stress‐activated protein kinase (SAPK)/c‐Jun N‐terminal (JNK), positively plays a part in the platelet‐derived growth factor‐BB‐
(PDGF‐BB‐) stimulated synthesis of interleukin‐6 (IL‐6), a potent bone resorptive agent, in osteoblast‐like MC3T3‐E1 cells while Akt and p70 S6 kinase negatively regulates the synthesis. In the present study, we investigated whether (‐)‐epigallocatechin gallate (EGCG), one of the major green tea flavonoids, affects the synthesis of IL‐6 in these cells and the mechanism. EGCG significantly reduced the IL‐6 synthesis and IL‐6 mRNA expression stimulated by PDGF‐BB, EGCG reduced the PDGF‐BB‐stimulated IL‐6 synthesis also in primary‐cultured osteoblasts. EGCG had no effect on the levels of osteocalcin and osteoprotegerin in MC3T3‐E1 cells. The PDGF‐BB‐induced autophosphorylation of PDGF receptor β was not suppressed by EGCG. The PDGF‐BB‐induced phosphorylation of p44/p42 MAP kinase and p38 MAP kinase was not affected by EGCG. On the other hand, EGCG markedly suppressed the PDGF‐BB‐induced phosphorylation of SAPK/JNK. Finally, the PDGF‐BB‐induced phosphorylation of Akt and p70 S6 kinase was not affected by EGCG. These results strongly suggest that EGCG inhibits the PDGF‐BB‐stimulated synthesis of IL‐6 via suppression of SAPK/JNK pathway in osteoblasts.
Best Proximity Pairs for Upper Semicontinuous Set-Valued Maps in Hyperconvex Metric Spaces
Authors: Amini-Harandi A. , Farajzadeh A. P. , O'Regan D. , Agarwal R. P.
Published: January 2009

A best proximity pair for a set-valued map "Equation missing" with respect to a map "Equation missing" is defined, and new existence theorems of best proximity pairs for upper semicontinuous set-valued maps with respect to a homeomorphism are proved in hyperconvex metric spaces.
Weak and Strong Convergence Theorems of an Implicit Iteration Process for a Countable Family of Nonexpansive Mappings
Authors: Nakprasit Kittikorn , Nilsrakoo Weerayuth , Saejung Satit
Published: January 2009

Using the implicit iteration and the hybrid method in mathematical programming, we prove weak and strong convergence theorems for finding common fixed points of a countable family of nonexpansive mappings in a real Hilbert space. Our results include many convergence theorems by Xu and Ori (2001) and Zhang and Su (2007) as special cases. We also apply our method to find a common element to the set of fixed points of a nonexpansive mapping and the set of solutions of an equilibrium problem. Finally, we propose an iteration to obtain convergence theorems for a continuous monotone mapping.
New Adaptive Algorithms for GOP Size Control with Return Channel Suppression in Wyner-Ziv Video Coding
Authors: Yaacoub Charles , Farah Joumana , Pesquet-Popescu Béatrice
Published: January 2009

We present novel algorithms for adaptive GOP size control in distributed Wyner-Ziv video coding, where an H.264 video codec is used for intracoding of key frames. The proposed algorithms rely on theoretical calculations to estimate the bit rate necessary for the successful decoding of Wyner-Ziv frames without the need for a feedback channel, which makes the system suitable for broadcasting applications. Additionally, in regions where H.264 intracoding outperforms Wyner-Ziv coding, the system automatically switches to intracoding mode in order to improve the overall performance. Simulations results show a significant gain in the average PSNR that can reach 3 dB compared to pure H.264 intracoding, and 0.8 dB compared to fixed-GOP Wyner-Ziv coding.
Residual Stress Fields due to Varying Tack Welds Orientation in Circumferentially Welded Thin-Walled Cylinders
Authors: Qureshi E. M. , Malik A. M. , Dar N. U.
Published: January 2009

The local, nonuniform heating and subsequent cooling during the welding processes causes complex thermal stress/strain fields to develop that finally leads to residual stresses, distortions, and their adverse consequences. Residual stresses are of prime concern to the industries producing weld-integrated structures around the globe because of their obvious potential to cause dimensional instability in welded structures, contribute to premature fracture/failure, along with the significant reduction in fatigue strength and in-service performance of the welded structures. Arc welding with single or multiple weld runs is an appropriate and cost effective joining method to produce high-strength structures in these industries. A multifield interaction in arc welding process makes it a complex manufacturing process. A number of geometric and process parameters are contributing to significant stress levels in arc-welded structures. In the present analysis, parametric studies are conducted for the effects of a critical geometric parameter, that is, tack weld on the corresponding residual stress fields in circumferentially welded thin-walled cylinders. Tack welds offer a considerable resistance to the shrinkage and the orientation, and size of tacks can alter altogether the stress patterns within the weldments. Hence, a critical analysis for the effects of tack weld orientation is desirable.