bluuebunny/crossref_metadata_2025 huggingface dataset:
The medium and the message of mental time travel
Authors: Tulving Endel , Kim Alice
Published: October 2007

We add one point to Suddendorf & Corballis's (S&C's) story of mental time travel: For the future success of this hot, new area of research, it is imperative to pay attention to the fundamental distinction between the general brain/mind capacity that makes possible conscious awareness of the past and the future (the “medium”), on the one hand, and specific expressions of this capacity in a large variety of future-related mental activities (the “message”), on the other.
Mental time travel across the disciplines: The future looks bright
Authors: Suddendorf Thomas , Corballis Michael C.
Published: October 2007

There is a growing interest in mental time travel in cognitive psychology, neuroscience, developmental psychology, comparative psychology, and evolutionary psychology. Here we review current issues in each of these disciplines. To help move the debates forward we name and distinguish 15 key hypotheses about mental time travel. We argue that foresight has for too long lived in the shadows of research on memory and call for further research efforts.
Indicators of forest ecosystem productivity and nutrient status across precipitation and temperature gradients in Hawaii
Authors: Idol Travis , Baker Patrick J. , Meason Dean
Published: October 2007

Precipitation and temperature are known to have important effects on forest productivity, but these effects may be strongly mediated through their influence on soil and leaf nutrients. We measured indicators of forest productivity and soil and leaf nutrients across independent gradients of precipitation and elevation/temperature in lower montane Hawaiian forests dominated by a single overstorey species, Acacia koa, situated on 1500–3000-y-old soils that were mixtures of volcanic ash and basalt. Stand basal area was highest at the wettest site, 2000 mm mean annual precipitation (MAP), and leaf N and P were lowest at the driest site, 1000 mm MAP. Soil N availability and leaf N concentration declined across an 850-m elevation gradient, but this was not correlated with stand basal area or soil organic matter content. Across all stands, basal area was negatively correlated with the exchangeable soil P fraction. As well, the soil C:N ratio was negatively correlated with both soil P availability and the size of the primary mineral P fraction. Soil P availability and weathering appear to be important determinants of soil organic matter quantity and quality. Overall, precipitation is the major driving force for forest productivity, but P weathering and availability play important roles in limiting productivity in wetter sites and in controlling soil organic matter dynamics in these N-fixing forests.
Post-fire succession on savanna habitats in the Okavango Delta wetland, Botswana
Authors: Heinl Michael , Sliva Jan , Murray-Hudson Michael , Tacheba Budzanani
Published: October 2007

Drying floodplains that were not inundated for more than 10 y were investigated to relate plant species and vegetation structure to time-since-fire for the southern Okavango Delta wetland in Botswana. The aims of the research were to study post-fire succession on savanna habitats in the Okavango Delta and to investigate the mechanisms behind vegetation changes with time-since-fire. We hypothesize that vegetation structure rather than species occurrence is affected by the fire event and that the driving forces of post-fire succession change from fire-driven to competition-driven with increasing time-since-fire. A total number of 153 study sites were investigated, representing areas of 2–12 y without a fire. Both woody and herbaceous plant species were recorded and cover/abundance values were measured. The vegetation changes with time-since-fire could be assigned to three different successional stages: (1) the post-fire conditions shortly after fire, supporting high species numbers due to open space and little competition; (2) the dominance of competitive perennial grass species (e.g. Urochloa mosambicensis) after 6–8 y; and (3) the enhanced establishment of woody species after about 10 y, creating new habitats in their vicinity. High species numbers were found after short and long fire-free periods, and different species occurred shortly after the fire event and at late stages of the post-fire succession. A variety of different inter-fire intervals is therefore expected to be responsible for sustaining plant species richness and habitat diversity in the study area. Post-fire succession could be described as not only being driven by the life history of the species, but also by seedbank dynamics and plant mobility in early successional stages and by competition and niche differentiation in late-successional stages.
Patterns of phosphorus, nitrogen and δ15N along a peat development gradient in a coastal mire, Panama
Authors: Troxler Tiffany G.
Published: October 2007

Differentiation of limiting nutrients within small spatial scales has been observed in coastal mangrove forests, but research on other tropical peatlands suggests it is a more widespread phenomenon. In the Changuinola mire of coastal Panama, oligotrophy was hypothesized to increase along a gradient of peat development (peat doming). Nutrient and carbon concentration of leaf tissue, soil, and soil porewater were characterised over a successive sequence of plant communities along the gradient. Soil phosphorus (P) and nitrogen (N) concentrations decreased from 1200 μg P g−1 and 27 mg N g−1 to 377 μg P g−1 and 22 mg N g−1 within 2.7 km into the mire interior. These changes coincided with an increase in soil and average leaf N:P molar ratios from 52–128 and 24–41, respectively. Soil P was strongly related to leaf P and soil N:P to foliar N:P. There was a wide range in δ15N values for canopy (4.0 to −9.4‰), Campnosperma panamense (4.0 to −7.8‰) and understorey (4.8 to −3.1‰) species. Foliar δ15N values of canopy species were strongly related to soil N:P, soil P and leaf P. The depleted foliar δ15N values appeared to be an effect of both the N atmospheric source and P limitation. Here, P limitation is likely associated with ombrotrophic conditions that developed as hydrologic inputs became dominated by precipitation.
Interaction network and the relationships between bromeliads and hummingbirds in an area of secondary Atlantic rain forest in southern Brazil
Authors: Piacentini Vítor de Queiroz , Varassin Isabela Galarda
Published: October 2007

The reciprocal importance of bromeliads and hummingbirds has been proposed for many years, even suggesting coevolution between these two groups. Nevertheless, data are lacking that allow a better test of the relationships involved. Here we investigate the relationship between bromeliads and hummingbirds in an area of secondary Atlantic rain forest in southern Brazil. The study examined the interactions among 12 species of bromeliad and 10 of hummingbird at Reserva Natural Salto Morato, Paraná state. The number of flowering species of bromeliad and the species richness and abundance of hummingbirds were quantified monthly between November 2004 and October 2005. Focal observations on each bromeliad species were made to determine the hummingbird visitors. Neither species richness nor abundance of hummingbirds were related to bromeliad phenology. Together with the monthly variation in visit frequency by a given pollinator to a given plant, these factors indicate a generalization in the use of bromeliads by hummingbirds and argue against tight coevolution. Ramphodon naevius and Thalurania glaucopis were the main pollinators in the community. Aechmea nudicaulis was the most generalist bromeliad species. The generalist species interacted with other generalists or with asymmetric specialists and there was no specialist–specialist interaction. This produced a strongly organized and nested matrix of interactions. This nestedness is similar to other plant-pollinators networks, supporting the hypothesis that the evolutionary relationship between bromeliads and hummingbirds is no stronger than that of other pollination networks.
A stable isotope study of a neotropical stream food web prior to the extirpation of its large amphibian community
Authors: Verburg Piet , Kilham Susan S. , Pringle Catherine M. , Lips Karen R. , Drake Dana L.
Published: October 2007

Rapid and massive amphibian population declines have been reported throughout upland areas of the Neotropics. The abundance and species richness of Neotropical amphibian communities suggest that losses of this magnitude are likely to have strong effects at the ecosystem level. To improve understanding of the implications of their loss we used stable isotope analysis to examine trophic relationships in an ecosystem in which amphibians are dominant in a second-order forest stream at 750 m asl in Parque Nacional Omar Torrijos Herrera, Panama. We analysed δ13C, δ15N and C:N ratios of major biotic components (basal resources, invertebrates, amphibians, fish and reptiles) in the stream and of the adjacent riparian food web. Tadpoles (mean δ15N = 4.49‰) and adult amphibians (mean δ15N = 5.45‰) were intermediate links in the aquatic and terrestrial food web respectively. High δ15N signatures identified fish as top predators in the aquatic food web and snakes and the toad Bufo as top predators in the terrestrial food web. Isotopic signatures clearly distinguished between trophic groups of tadpoles: microbial feeders (Centrolenidae, δ15N range = 0.91–3.05‰), herbivores (Rana and Hyla, δ15N range = 4.74–5.15‰) and neuston feeders (Colostethus, δ15N range = 5.31–6.40‰). Dependence on autotrophic production was indicated by enriched signatures of carbon isotopes in pool dwellers versus those that reside in faster-flowing sections of the stream. High nitrogen concentrations in detrital matter (average 0.8%, C:N = 10.3) suggested that grazing tadpoles enhanced nitrogen fluxes and improved the quality of organic matter available to detritivores.
Impacts of habitat fragmentation on genetic diversity in a tropical forest butterfly on Borneo
Authors: Benedick Suzan , White Thomas A. , Searle Jeremy B. , Hamer Keith C. , Mustaffa Nazirah , Khen Chey Vun , Mohamed Maryati , Schilthuizen Menno , Hill Jane K.
Published: October 2007

Many areas of rain forest now exist as habitat fragments, and understanding the impacts of fragmentation is important for determining the viability of populations within forest remnants. We investigated impacts of forest fragmentation on genetic diversity in the butterfly Mycalesis orseis (Satyrinae) in Sabah (Malaysian Borneo). We investigated mtDNA diversity in 90 individuals from ten forest sites typical of the sizes of forest remnants that currently exist in the region. Nucleotide diversity declined with increasing isolation of remnants, but there was no effect of remnant size or population size, and haplotype diversity was similar among sites. Thus, approximately 50 y after forest fragmentation, few changes in genetic diversity were apparent and remnants apparently supported genetically viable populations of this butterfly. Many studies have shown that responses of species to habitat fragmentation usually follow a time delay, and so we developed a Monte Carlo simulation model to investigate changes in genetic diversity over time in small remnants. Model output indicated a substantial time delay (> 100 y) between fragmentation and genetic erosion, suggesting that, in the smallest study remnants, an increased risk of extinction from reduced genetic diversity is likely in the longer term.
Nutritional composition of the diet of the gorilla (Gorilla beringei): a comparison between two montane habitats
Authors: Rothman Jessica M. , Plumptre Andrew J. , Dierenfeld Ellen S. , Pell Alice N.
Published: October 2007

The mountain gorilla (Gorilla beringei beringei) lives in two geographically separated populations, Bwindi Impenetrable National Park, Uganda and in three national parks spanning the Virunga mountain region in Rwanda, Democratic Republic of Congo, and Uganda. The altitude, climate and plant composition of these habitats differ. Our goal was to compare the diets of gorillas living in each of these habitats. The nutrients in staple foods and in the diets of individuals in a group of gorillas in Bwindi (N = 12 individuals) and a group in the Virungas (N = 7 individuals) were compared to determine if differences in dietary composition affected concentrations of nutrients in their diets. At both sites gorilla diets consisted primarily of herbaceous leaves, but the diet of Bwindi gorillas contained more tree leaves, fruit, pith and dry wood, and fewer stems. Despite differences in habitat and dietary composition, the nutrient concentrations in both gorilla diets were remarkably similar. On a dry matter basis, the diets and staple foods of Bwindi and Virunga gorillas contained similar concentrations of crude protein (CP), fibre (NDF) and non-structural carbohydrates (TNC). Bwindi gorillas ate diets containing 18% CP, 43% NDF and 19% TNC on a dry-matter basis, while the diets of the Virunga gorillas contained 17% CP, 41% NDF and 18% TNC. Our results demonstrate that gorillas consume diets that differ by plant species and part, but contain similar concentrations of nutrients. This suggests that classifying animals by broad dietary strategy (e.g. frugivory and folivory) does not provide a reliable indicator of the nutritional quality of their diet, and that our previous assumptions about these categories should be re-evaluated.
Preface
Authors: ESCARDÓ MARTÍN , JUNG ACHIM , STREICHER THOMAS
Published: October 2007

This is the second part of a special issue in honour of Klaus Keimel – the first part appeared in Mathematical Structures in Computer Science16 (2). This second part consists of a single paper by John Longley, which could not be included in the earlier issue for reasons of size.
Parthenogenetic activation of bovine oocytes using single and combined strontium, ionomycin and 6-dimethylaminopurine treatments
Authors: Méo S.C. , Yamazaki W. , Ferreira C.R. , Perecin F. , Saraiva N.Z. , Leal C.L.V. , Garcia J.M.
Published: October 2007

In vitro-matured (IVM) bovine oocytes were activated with single and combined treatments of strontium (S), ionomycin (I) and 6-DMAP (D). Using oocytes IVM for 26 h, we observed that activation altered cell cycle kinetics (faster progression, MIII arrest, or direct transition from MII to pronuclear stage) when compared toin vitrofertilization. The effect of oocyte age on early parthenogenesis was assessed in oocytes IVM for 22, 26 and 30 h. Better results in pronuclear development were obtained in treatments ISD (81.7%) at 22 h; D (66.7%), IS (63.3%), ID (73.3%) and ISD (76.7%) at 26 h; and D (86.7%), IS (85.0%) and ID (78.3%) at 30 h. Higher cleavage occurred on ISD (80.0%) at 22 h; ID (83.3%) and ISD (91.7%) at 26 h; and I (86.7%), IS (90.0%), ID (85.0%) and ISD (95.0%) at 30 h. More blastocysts were achieved in ID (25.0%) and ISD (18.3%) at 22 h; and in ID at 26 h (45.0%) and 30 h (50.0%). We also observed that IS allowed higher haploid (77.4%) embryonic development, whilst ID was better for diploid (89.1%) development. It was concluded that association of S and D without I was not effective for blastocyst development; treatments using S were less influenced by oocyte age, but when S was associated with D there was a detrimental effect on aged oocytes; treatment ISD promoted higher activation and cleavage rates in young oocytes and ID protocol was the best for producing blastocysts.
In vitro maturation, in vitro fertilization and embryonic development of canine oocytes
Authors: Lee S.R. , Kim B.S. , Kim J-W. , Kim M.O. , Kim S.H. , Yoo D.H. , Shin M-J. , Park Y.S. , Lee S. , Park Y.B. , Ha J.H. , Ryoo Z.Y.
Published: October 2007

In this study we have investigated the efficiency of in vitro maturation (IVM) as a basic way to study the development of canine oocytes after in vitro fertilization (IVF). We decided, therefore, to perform two-part experiments. Firstly, experiment I compared the effects of TCM199 without fetal bovine serum (FBS) with TCM199 supplemented with 5% FBS on the in vitro nuclear maturation rate of canine oocytes. For the efficiency of meiotic development to the metaphase II (MII) stage, we found that 4.7% (4/64) of all oocytes grown in TCM199 without FBS developed to the MII stage compared with only 1.7% (1/59) of those grown in TCM199 with 5% FBS for 48 h. Therefore, FBS did not increase in vitro nuclear maturation. In experiment II, the cleavage rate of canine oocytes used for IVF was investigated following heparin treatment. Canine oocytes were fertilized in four groups: Fert–TALP medium without heparin (Fert I) or Fert–TALP medium supplemented with 10, 20 or 30 µg/ml heparin (Fert II, Fert III, Fert IV, respectively). Oocytes that were grown for 24 h in Fert I following fertilization showed the highest rate of all of the groups, 6.5% (5/77) and developed to the early morula stage. Markedly, the oocytes cultured in Fert I for 24 h following insemination had a higher rate of embryonic development than other groups. We can assert that, unlike findings in other mammals, heparin treatment in canine IVF does not increase the efficiency of the fertilization rate and is therefore not an important factor.
Long-term follow-up of porcine male germ cells transplanted into mouse testes
Authors: Choi Y-J. , Park J-K. , Lee M-S. , Ahn J.D. , Hwang K-C. , Song H. , Kim J-H.
Published: October 2007

This study investigated the effect of increased phylogenetic distance on the outcome of spermatogonial transplantation, with porcine donors and mice recipients. It was designed to develop a technique for detecting foreign donor cells in recipient animals. Porcine male germ cells were harvested from postnatal male testes and incubated with the lipophilic membrane dye PKH-26. For transplantation, approximately 106PKH-26-labelled porcine male germ cells were injected into the efferent ducts of mouse testes. Animals were sacrificed at post-graft days 1, 10, 30, 45, 60 and 150 (n= 5 each). Serial frozen sections of explanted testes were prepared for detecting labelled cells. Transplanted porcine donor cells were easily detected in the recipient tubules for 8 weeks. After transplantation, we could detect both incorporation into the basement membrane and differentiation of grafted porcine donor cells by our double detection system, using PKH staining and slide PCR. However, our RT-PCR and apoptosis results revealed that most of the grafted porcine male donor cells could not differentiate past early-meiotic spermatocytes. We could induce partial differentiation of xenografted porcine donor cells in mouse testes, but not full induction of spermatogenesis. We have developed a very reliable technique for detecting foreign donor cells in recipient animals using a combination of PKH staining and slide PCR methods. Our results provide a valuable experimental model for applying and evaluating this technology in other species.
Bisphosphonates and prevention of metastases: the AZURE study
Authors: Burkinshaw R. , Thorpe H. , Coleman R.
Published: October 2007

Most patients present with disease that appears to be confined to the breast. However, a significant proportion of women will go on to develop metastatic breast cancer with bone being the most frequent site of distant relapse. The bone microenvironment provides a fertile soil for circulating metastatic cells as resorbing bone releases growth factors that are thought to attract circulating cancer cells to the bone surface and facilitate their growth and proliferation. These infiltrating tumour cells in turn produce bone cell-activating factors, which lead to increased bone resorption and further release of growth factors in a ‘vicious cycle’. The third-generation bisphosphonate zoledronic acid is a potent inhibitor of osteoclast-mediated bone resorption. It also has effects on numerous processes in the metastatic cascade, with in vitro and animal studies showing synergistic antitumour effects with a range of cytotoxic and endocrine treatments. The addition of zoledronic acid to adjuvant therapy could therefore be a therapeutic strategy of potential importance.

To investigate this, the AZURE trial was designed to determine whether adjuvant zoledronic acid improves the disease-free and bone metastasis-free survival of women with stage II/III breast cancer. Recruitment of 3300 subjects was completed in January 2006. First efficacy data are expected in 2008. There is a potential for synergistic action with chemotherapy to manifest as enhanced toxicity. Reassuringly, initial safety data show that zoledronic acid is well tolerated and can be safely combined with adjuvant chemotherapy without any increase in myelotoxicity or effect on dose intensity.
A model of the French pension reserve fund: what could be the optimal contribution path rate?
Authors: BERGER CHARLIE , LAVIGNE ANNE
Published: October 2007

Current and expected demographic and economic trends are likely to jeopardize the financial sustainability of the French retirement pension scheme, which mainly operates on a pay-as-you-go basis. In 1999, the French government set up a Pension Reserve Fund (Fonds de réserve pour les retraites, FRR) the main objective of which was to introduce some public funding in the PAYG basic pension scheme to cope with its expected financial unsustainability within the next decade. This paper presents some simulation results on the projected evolution of the French Pension Reserve Fund under various assumptions. The main idea is to optimize the profile of the trend in contribution rates needed to meet the objective of a balanced basic pension scheme over the period 2006–2050. Our simulations show that under plausible assumptions the amount of funding is likely to be less important than the Government expected at the FRR set up, about 100 billion euros. Some stress tests show that severe shocks on financial markets may dramatically affect the funding profile of the FRR beyond 2045.
Demography and investment behavior of pension funds: evidence for Switzerland
Authors: GERBER DAVID S. , WEBER RENÉ
Published: October 2007

This paper focuses on the nexus between pension funds' balance sheet liabilities, reflecting their age profile and payments obligations, and the investment behavior and costs of these funds. The context of the analysis is the stringent regulatory framework and the highly fragmented and heterogeneous pension fund landscape in Switzerland. Detailed data from the Swiss Pension Statistic are analyzed using multivariate OLS-regressions. The evidence shows that a younger age structure and lower short-term benefits payouts are related to a higher share of equities and lower real estate holdings. Legal form, pension plan type, and size are important for administrative costs. The findings support the view that aging may lead to increased risk aversion and thus to a lower engagement of institutional investors in equities.
An analysis of money's worth ratios in Chile
Authors: THORBURN CRAIG , ROCHA ROBERTO , MORALES MARCO
Published: October 2007

Empirical analyses of annuities markets have been limited to a few developed countries and restricted by data limitations. Chile provides excellent conditions for research on annuities due to the depth of its market and the availability of data. The paper utilizes an extensive dataset on individual annuities to examine econometrically a measure of market performance – money's worth ratios (MWRs), or the ratio of the expected present value of annuity payments to the premium. The results show that annuitants in Chile have generally got a good deal for their premiums, as indicated by MWRs higher than one and also higher than those estimated for other countries. The difference between Chile and other countries is striking considering that annuities in Chile are indexed to prices. The wide range of indexed instruments in Chile, allowing providers to hedge their risks while extracting higher returns, helps explain the difference. The high degree of market competition has also contributed to this outcome. Efforts to improve market transparency through a new electronic quotation system have decreased the dispersion of MWRs. Finally, MWRs tend to decrease for contracts with longer durations, reflecting pricing for higher longevity and reinvestment risks. These results are consistent with separate research on the annuity rate, and indicate the need to ensure competition and market transparency, as well as to develop appropriate financial instruments for providers in order to ensure good outcomes for annuitants.
Aeromagnetic anomalies reveal hidden tectonic and volcanic structures in the central sector of the Aeolian Islands, southern Tyrrhenian Sea, Italy
Authors: De Ritis Riccardo , Ventura Guido , Chiappini Massimo
Published: October 2007

Salina Island (Italy) in the central Aeolian chain is the northernmost volcanic structure of an elongated ridge on a regional shear zone with NNW‐SSE strike‐slip faults and second‐order N‐S and NE‐SW faults. Modeling of high‐resolution, low‐altitude aeromagnetic data collected in 2003 and 2005 using volcanological data constraints reveals the inner structure of the Salina volcanoes and surrounding marine regions. Regional negative anomalies overlie E‐W elongated sedimentary basins related to the early Pliocene‐Pleistocene opening of the southern Tyrrhenian Sea. These negative anomalies flank positively magnetized crust of Salina and seamounts off its eastern coast where the shorter‐wavelength anomalies map late Pleistocene‐Holocene volcanic conduits, dikes, and faults. The magnetic and volcanological data indicate that the early (circa 168–100 ka) basaltic to andesitic Salina volcanism developed along N‐S and NE‐SW tectonic faults, whereas the more recent andesitic lavas and rhyolitic pyroclastics (circa 100–13 ka) were emitted by vents related to the main NW‐SE faults. The tectonic structures also controlled the location of the seamounts around the island and the geometry of the volcano‐tectonic collapses. Salina volcanism was emplaced on a NNW‐SSE tear fault of the presently developing roll‐back slab in the southern Tyrrhenian Sea.
Radon daily signals in the Elat Granite, southern Arava, Israel
Authors: Steinitz G. , Piatibratova O. , Barbosa S. M.
Published: October 2007

High time resolution monitoring of radon (=222Rn) in three boreholes, 4, 10 and 53 m deep, along a 0.6 km transect is carried out in massive granite in southern Israel. Three components of variation occur in the measured signal (MS) ‐ seasonal radon (SR ‐ periodic), multiday (MD), and daily radon (DR ‐ periodic). Temporal variation of the components suggests an association between the overall level of the long‐term variation and the amplitude of the daily variation. The daily mean level of radon and the daily standard deviation vary periodically throughout the year. Time offsets occur among time series of the MS and were investigated also for the MD and DR components, using consecutive 20‐day intervals spanning +900 days. The resulting time series show that systematic time offsets occur, whereby the radon signal always occurs first at the easternmost site. The MD shows a gradually varying lag of 0–12 h, and the DR a stable 1–3 h lag. Spectral analysis shows that diurnal (24‐h) and semidiurnal (12‐h) periodic components characterize the DR. The amplitudes of these components exhibit regular temporal variation having a seasonal pattern. The ratios of co‐occurring amplitudes of these components define a linear pattern indicating a fundamental statistical property in the frequency domain of the radon time series. The results indicate that unrecognized dynamic processes are driving the radon signal in the subsurface regime of the pluton, suggesting new prospects for radon behavior in the frame of interacting geodynamic (tectonic?) and Earth‐Sun system related processes.
The dynamical response of the middle atmosphere to the tropospheric solar signal
Authors: Berg P. , Christiansen B. , Thejll P. , Arnold N.
Published: October 2007

To assess a possible solar modulation of the planetary waves, the 300 hPa geopotential height of the two major reanalysis data sets, NCEP/NCAR and ERA40, is studied for the difference between years of solar maximum and minimum activity for three solar cycles in the period 1963–1999. We find a significant positive difference over the North Pacific ocean for December through February which resembles that found in sea level pressures in earlier studies. Furthermore, there are statistically significant amplitude differences in the climatological state of the first two planetary waves extracted from the geopotential heights. We also perform a model study of the middle atmospheric response to the tropospheric solar signal. The 300 hPa geopotential height is used as the lower boundary in a middle atmosphere model which is run with a constant solar cycle minimum radiative forcing, so that only the lower boundary is forcing the middle atmosphere. The zonal wind and temperature at 300–0.01 hPa from the model experiment are studied in boreal winter for the same years that were studied in the geopotential height analysis. Differences of the means of the two data sets reproduce the structure and amplitude seen in observations and in reanalysis data. Whether this is a direct effect of the solar forcing of the troposphere or a feedback coupling of the solar forcing of the stratosphere is not presently clear, but the modulation of the tropospheric planetary waves seems to be important for the observed solar modulation of the stratosphere.
Using EOF analysis to qualitatively analyze, and identify inhomogeneities in, data from ground‐based aerosol monitoring instruments
Authors: Gianelli S. M. , Carlson B. E. , Lacis A. A.
Published: October 2007

Empirical Orthogonal Function (EOF) analysis is performed on ground‐based shadowband radiometer and Sun photometer data. The data come from Multifilter Rotating Shadowband Radiometer (MFRSR) instruments located at the central and extended facilities of the Southern Great Plains (SGP) research site of the Department of Energy's Atmospheric Radiation Measurement (ARM) program, as well as the Rotating Shadowband Spectroradiometer (RSS) 102 and 105 and the CIMEL Sun photometer CSPHOT located at the central facility at SGP. The EOFs show the variability in total aerosol optical depth and provide some qualitative information on the separation of the coarse and fine aerosol modes. In addition, as has been demonstrated previously with satellite data, EOF analysis also exposes several flaws and inconsistencies within the ground‐based data sets. These inhomogeneities include optical depth anomalies in some MFRSR filters, wavelength shifts in the RSS, and problems with the data transmitter of the CIMEL instrument. Therefore EOF analysis is shown to be a quick and effective means not only of assessing the general aerosol behavior in the air above a particular monitoring instrument, but also of identifying both known and unanticipated influences on the data coming from within the instrument itself.
The Unified Gravel‐Sand (TUGS) Model: Simulating Sediment Transport and Gravel/Sand Grain Size Distributions in Gravel‐Bedded Rivers
Authors: Cui Yantao
Published: October 2007

This paper presents The Unified Gravel‐Sand (TUGS) model that simulates the transport, erosion, and deposition of both gravel and sand. TUGS model employs the surface‐based bed load equation of Wilcock and Crowe (2003) and links grain size distributions in the bed load, surface layer, and subsurface with the gravel transfer function of Hoey and Ferguson (1994) and Toro‐Escobar et al. (1996), a hypothetical sand transfer function, and hypothetical functions for sand entrainment/infiltration from/into the subsurface. The model is capable of exploring the dynamics of grain size distributions, including the fractions of sand in sediment deposits and on the channel bed surface, and is potentially useful in exploring gravel‐sand transitions and reservoir sedimentation processes. Simulation of three sets of large‐scale flume experiments indicates that the model, with minor adjustment to the Wilcock‐Crowe equation, excellently reproduced bed profile and grain size distributions of the sediment deposits, including the fractions of sand within the deposits. Simulation of a flushing flow experiment indicated that the sand entrainment function is potentially capable of simulating the short‐term processes such as flushing flow events.
Dating degassed groundwater with 3H/3He
Authors: Visser Ate , Broers Hans Peter , Bierkens Marc F. P.
Published: October 2007

The production of gases in groundwater under contaminated locations by geochemical and biological processes is not uncommon. Degassing of these gases from groundwater and repartitioning of noble gases between water and gas phase distorts groundwater dating by 3H/3He. We observed noble gas concentrations below atmospheric equilibrium in 20 out of 34 groundwater samples from agriculturally polluted sandy areas in the Netherlands. From the absence of nitrate in degassed samples, we conclude that denitrification causes degassing. The 22Ne/20Ne ratios show that degassing had attained solubility equilibrium and had not caused isotopic fractionation by diffusion. To correct for the loss of tritiogenic 3He due to degassing, we present a single‐step equilibrium degassing model. We use the total dissolved gas pressure at the monitoring screen to estimate the depth and timing of degassing, which is essential to estimate travel times from degassed samples. By propagating the uncertainties in the underlying measurements and assumptions through the travel time calculations, we found a travel time uncertainty of 3 years (a). We therefore conclude that 3H/3He dating can produce valuable information on groundwater flow even at sites with strong degassing.
Complex evolution of transient slip derived from precise tremor locations in western Shikoku, Japan
Authors: Shelly David R. , Beroza Gregory C. , Ide Satoshi
Published: October 2007

Transient slip events, which occur more slowly than traditional earthquakes, are increasingly being recognized as important components of strain release on faults and may substantially impact the earthquake cycle. Surface‐based geodetic instruments provide estimates of the overall slip distribution in larger transients but are unable to capture the detailed evolution of such slip, either in time or in space. Accompanying some of these slip transients is a relatively weak, extended duration seismic signal, known as nonvolcanic tremor, which has recently been shown to be generated by a sequence of shear failures occurring as part of the slip event. By precisely locating the tremor, we can track some features of slip evolution with unprecedented resolution. Here, we analyze two weeklong episodes of tremor and slow slip in western Shikoku, Japan. We find that these slip transients do not evolve in a smooth and steady fashion but contain numerous subevents of smaller size and shorter duration. In addition to along‐strike migration rates of ∼10 km/d observed previously, much faster migration also occurs, usually in the slab dip direction, at rates of 25–150 km/h over distances of up to ∼20 km. We observe such migration episodes in both the updip and downdip directions. These episodes may be most common on certain portions of the plate boundary that generate strong tremor in intermittent bursts. The surrounding regions of the fault may slip more continuously, driving these stronger patches to repeated failures. Tremor activity has a strong tidal periodicity, possibly reflecting the modulation of slow slip velocity by tidal stresses.
Parametric decay of circularly polarized Alfvén waves in the radially expanding solar wind
Authors: Tanaka Shin , Ogino Tatsuki , Umeda Takayuki
Published: October 2007

We present a magnetohydrodynamic (MHD) simulation study of the parametric decay of the circularly polarized Alfvén waves propagating in the radial outflow of the solar wind. Assuming the transonic wind solution as an initial condition, we continuously injected monochromatic circularly polarized Alfvén waves from the inner boundary at the lower corona, and simulated the wave propagation. The injected Alfvén waves are subject to the parametric decay, and density fluctuations in the solar wind plasma grow rapidly at a specific region. The location of the most unstable region depends on the amplitude and frequency of injected Alfvén waves. We found that the unstable region of simulation results can be well estimated by considering a localized dispersion relation in the frame of reference moving with the background solar wind.
Sources, transport, and distributions of plasma sheet ions and electrons and dependences on interplanetary parameters under northward interplanetary magnetic field
Authors: Wang Chih‐Ping , Lyons Larry R. , Nagai Tsugunobu , Weygand James M. , McEntire Richard W.
Published: October 2007

We have investigated the Geotail data statistically to understand the particle sources, transport, and spatial distributions of the plasma sheet ions and electrons of different energies during northward interplanetary magnetic field (IMF), and their dependences on the solar wind density (Nsw), the solar wind speed (Vsw), and the magnitude of the northward IMF Bz (∣Bz,IMF∣). We find that the plasma sheet becomes colder and denser, indicating a larger increase in the cold than in the hot population, with increasing Nsw or ∣Bz,IMF∣ or with decreasing Vsw. The cold population dominates the region near the flanks while the hot population dominates the near‐midnight region, which is consistent with the plasma sheet plasma being a mixture of cold particles coming from the flanks and hot particles from the distant‐tail. The phase space densities show that the flank source strongly depends on ∣Bz,IMF∣, while the tail source strongly depends on Vsw. Cold particles from the dawn flank to midnight increase significantly with decreasing Vsw, but no significant changes are seen near the dusk flank, suggesting a dependence of the solar wind entry through the dawn flank on Vsw. The comparisons between the distributions of the phase space density and the electric and magnetic drift paths estimated from the observations indicate that the thermal and high‐energy particles are mainly transported by electric and magnetic drift, while other transport mechanisms, such as diffusion, may play a role in transporting the low energy particles from the flank sources to midnight.
Implication of seismic attenuation for gas hydrate resource characterization, Mallik, Mackenzie Delta, Canada
Authors: Bellefleur G. , Riedel M. , Brent T. , Wright F. , Dallimore S. R.
Published: October 2007

Wave attenuation is an important physical property of hydrate‐bearing sediments that is rarely taken into account in site characterization with seismic data. We present a field example showing improved images of hydrate‐bearing sediments on seismic data after compensation of attenuation effects. Compressional quality factors estimated from zero‐offset Vertical Seismic Profiling data acquired at Mallik, Northwest Territories, Canada, demonstrate significant wave attenuation for hydrate‐bearing sediments. These results are in agreement with previous attenuation estimates obtained from sonic logs and crosshole data at different frequency intervals. The application of an inverse Q‐filter to compensate attenuation effects of permafrost and hydrate‐bearing sediments improved the resolution of surface 3D seismic data and its correlation with log data, particularly for the shallowest gas hydrate interval. Compensation of the attenuation effects of the permafrost likely explains most of the improvements for the shallow gas hydrate zone. Our results show that characterization of the Mallik gas hydrates with seismic data not corrected for attenuation would tend to overestimate thicknesses and lateral extent of hydrate‐bearing strata and hence, the volume of hydrates in place.
Evaluation and improvement of AMSU precipitation retrievals
Authors: Vila Daniel , Ferraro Ralph , Joyce Robert
Published: October 2007

The Advanced Microwave Sounding Unit‐B (AMSU‐B) high frequency channels (89 and 150‐GHz) provide the ability to detect the scattering associated with precipitation sized ice particles and, indirectly with precipitation rate. Despite the fact that AMSU (a “sounder”) wasn't designed for rainfall retrieval, many studies show that it is possible to use this information for precipitation retrieval and therefore, many researchers use them in blending techniques to estimate rainfall at global scale. The main advantage of this approach is the availability of three NOAA POES satellites spaced approximately 4 h apart with a spatial resolution of 16 km at nadir and a wider swath than SSMI (2200 km), offers an excellent opportunity to reduce the errors associated with the inadequate sample of the diurnal cycle; while the weakness of this technique are related with its present inability to retrieve rain that has little or no ice; and with the cross‐scan characteristics of the instrument (different footprints for different local zenithal angles). This situation tends to generate, in the first case, much less rain coverage over ocean than other algorithms based on emission techniques and a shift in the frequency distribution for low zenithal angles in the second case. An improvement to the current scattering based algorithm that uses cloud liquid water content (over ocean only) and the local zenithal angle will be developed and tested in this paper. In particular, the application of the proposed correction scheme produces a more realistic rainfall amount distribution function (especially over the tropics) and a light increase of rainfall occurrence in midlatitudes. The improvement is demonstrated by both global and regional studies over land and ocean.
Aerosol forcing, climate response and climate sensitivity in the Hadley Centre climate model
Authors: Jones Andy , Haywood James M. , Boucher Olivier
Published: October 2007

An atmosphere/mixed‐layer‐ocean climate model is used to investigate the climate responses to forcing by 1860–2000 changes in anthropogenic sulfate, biomass‐burning and black carbon aerosols, and how they compare with the effect of doubling CO2. While the patterns of temperature response from sulfate and black carbon aerosols are similar and reveal high sensitivity at high latitudes in the northern hemisphere, they are significantly different to that due to CO2 which shows high latitude sensitivity in both hemispheres, and to biomass‐burning aerosols which shows a much more uniform temperature response. Climate sensitivity, the response of natural primary aerosols, and the degree to which forcings and responses are additive, are also investigated. The sum of the separate temperature and precipitation responses to each aerosol is found to be remarkably similar to that obtained if all aerosols are changed simultaneously.
Pore‐scale simulation of dispersion and reaction along a transverse mixing zone in two‐dimensional porous media
Authors: Acharya Ram C. , Valocchi Albert J. , Werth Charles J. , Willingham Thomas W.
Published: October 2007

Several studies have demonstrated that the success of natural and engineered in situ remediation of groundwater pollutants relies on the transverse mixing of reactive chemicals or nutrients along plume margins. Efforts to predict reactions in groundwater generally rely on dispersion coefficients obtained from nonreactive tracer experiments to determine the amount of mixing, but these coefficients may be affected by spreading, which does not contribute to reaction. Mixing is controlled only by molecular diffusion in pore spaces, and the length scale of transverse mixing zones can be small, often on the order of millimeters to centimeters. We use 2D pore‐scale simulation to investigate whether classical transverse dispersion coefficients can be applied to model mixing‐controlled reactive transport in three different porous media geometries: periodic, random, and macroscopically trending. The lattice‐Boltzmann method is used to solve the steady flow field; a finite volume code is used to solve for reactive transport. Nonreactive dispersion coefficients are determined from the transverse spreading of a conservative tracer. Reactive dispersion coefficients are determined by fitting a continuum model which calculates the total product formation as a function of distance to the results from our pore scale simulation. Nonreactive and reactive dispersion coefficients from these simulations are compared. Results indicate that, regardless of the geometrical properties of the media, product formation can be predicted using transverse dispersion coefficients determined from a conservative tracer, provided dispersion coefficients are determined beyond some critical distance downgradient where the plume has spread over a sufficiently large transverse distance compared to the mean grain diameter. This result contrasts with other studies where reactant mixing was controlled by longitudinal hydrodynamic dispersion; in those studies longitudinal dispersion coefficients determined from nonreactive tracer experiments over‐estimated the extent of reaction and product formation. Additional work is called for in order to confirm that these findings hold for a wider variety of grain sizes and geometries.
The roles of the prostaglandin D2receptors DP1and CRTH2 in promoting allergic responses
Authors: Pettipher R
Published: October 2007

Prostaglandin D2(PGD2) is produced by mast cells, Th2 lymphocytes and dendritic cells and has been detected in high concentrations at sites of allergic inflammation. PGD2exerts its inflammatory effects through high affinity interactions with the G protein coupled receptors DP1and chemoattractant‐homologous receptor expressed on Th2 cells (CRTH2, also known as DP2). DP1and CRTH2 act in concert to promote a number of biological effects associated with the development and maintenance of the allergic response. During the process of allergen sensitization, DP1activation may enhance polarization of Th0 cells to Th2 cells by inhibiting production of interleukin 12 by dendritic cells. Upon exposure to allergen in sensitized individuals, activation of DP1may contribute to the long lasting blood flow changes in the target organ. CRTH2 is expressed by Th2 lymphocytes, eosinophils and basophils and may mediate the recruitment of these cell types during the late phase allergic response. The role played by CRTH2 in promoting the production of Th2 cytokines and IgE make antagonism of this receptor a particularly attractive approach to the treatment of chronic allergic disease.

British Journal of Pharmacology(2008)153, S191–S199; doi:10.1038/sj.bjp.0707488; published online 29 October 2007