bluuebunny/crossref_metadata_2025 huggingface dataset:
LSST: Comprehensive NEO detection, characterization, and orbits
Authors: Ivezić Željko , Tyson J. Anthony , Jurić Mario , Kubica Jeremy , Connolly Andrew , Pierfederici Francesco , Harris Alan W. , Bowell Edward ,   the LSST Collaboration
Published: May 2007

The Large Synoptic Survey Telescope (LSST) is currently by far the most ambitious proposed ground-based optical survey. With initial funding from the National Science Foundation (NSF), Department of Energy (DOE) laboratories, and private sponsors, the design and development efforts are well underway at many institutions, including top universities and national laboratories. Solar System mapping is one of the four key scientific design drivers, with emphasis on efficient Near-Earth Object (NEO) and Potentially Hazardous Asteroid (PHA) detection, orbit determination, and characterization. The LSST system will be sited at Cerro Pachon in northern Chile. In a continuous observing campaign of pairs of 15 s exposures of its 3,200 megapixel camera, LSST will cover the entire available sky every three nights in two photometric bands to a depth of V=25 per visit (two exposures), with exquisitely accurate astrometry and photometry. Over the proposed survey lifetime of 10 years, each sky location would be visited about 1000 times, with the total exposure time of 8 hours distributed over several broad photometric bandpasses. The baseline design satisfies strong constraints on the cadence of observations mandated by PHAs such as closely spaced pairs of observations to link different detections and short exposures to avoid trailing losses. Due to frequent repeat visits LSST will effectively provide its own follow-up to derive orbits for detected moving objects.

Detailed modeling of LSST operations, incorporating real historical weather and seeing data from Cerro Pachon, shows that LSST using its baseline design cadence could find 90% of the PHAs with diameters larger than 250 m, and 75% of those greater than 140 m within ten years. However, by optimizing sky coverage, the ongoing simulations suggest that the LSST system, with its first light in 2013, can reach the Congressional mandate of cataloging 90% of PHAs larger than 140m by 2020. In addition to detecting, tracking, and determining orbits for these PHAs, LSST will also provide valuable data on their physical and chemical characteristics (accurate color and variability measurements), constraining PHA properties relevant for risk mitigation strategies. In order to fulfill the Congressional mandate, a survey with an etendue of at least several hundred m2deg2, and a sophisticated and robust data processing system is required. It is fortunate that the same hardware, software and cadence requirements are driven by science unrelated to NEOs: LSST reaches the threshold where different science drivers and different agencies (NSF, DOE and NASA) can work together to efficiently achieve seemingly disjoint, but deeply connected, goals.
NEO-related scientific and outreach activities at KLENOT
Authors: Tichá Jana , Tichý Miloš , Kočer Michal
Published: May 2007

In the recent times, there has been a noticeable increase in interest about NEOs. In the light of results of recent NEO surveys the need for continuous follow-up astrometry to secure the orbits of the discovered bodies has risen.

The Klet' Observatory Near Earth and other Unusual Objects Observation Team and Telescope, project KLENOT, started in 2002. It is dedicated to confirmation, follow-up, and recovery of NEOs. For this task the 1.06-m KLENOT telescope, equipped with a high-efficiency CCD is used. Since it was set in service in March 2002, a significant number of results have been obtained. For instance, 10,000 positions have been determined, more than 400 confirmations made, including 16 recoveries and 104 Virtual Impactors measured.

An important part of NEO search is the discovery of comets. Therefore an inseparable component of NEO follow-up includes the detection of possible cometary features of newly discovered bodies and the confirmation of Near Earth Comets (NEC).

In the next decade, surveys will be characterized by several aspects. Pan-STARRS opens the question whether “classical” confirmation and early follow-up of newly discovered NEO candidates will be necessary by others, and we discuss the need for possible changes in existing system of follow-up process. The most important challenge for follow-up will likely become the NEOs which are in urgent need of astrometric positions over longer arcs including Virtual Impactors, radar, and mission targets. The observing strategies and obtained results of the KLENOT Project will be presented as well as future plans will be discussed.

One of the most important duties of NEOs scientists and research institutions is to maintain contact with the public. NEO related issues have outstanding educational value and outreach potential. Nowadays the Internet has proved itself to be an excellent mean of bringing NEO knowledge to a wider audience.
Astrometry of small Solar System bodies at the Molėtai observatory
Authors: Černis K. , Zdanavičius J. , Zdanavičius K. , Tautvaišienė G.
Published: May 2007

We describe an observational project devoted to astrometric observations of Near-Earth Objects (NEO), main belt asteroids and comets at the Molėtai Observatory, Lithuania. Exposures are obtained with the two telescopes of the observatory: 0.35/0.50 m f/3.5 Maksutov telescope and the 1.65 m reflector with focal reductor f/3.1 and CCD camera. The results of more than 10,000 positions of asteroids and comets have been published in the Minor Planet Circulars and Minor Planet Electronic Circulars. During the 2001–2006 period 130 new asteroids were discovered. The latest discovery is the high-inclination asteroid 2006 SF77 belonging to the NEO Aten group.
The nature of asteroid Itokawa revealed by Hayabusa
Authors: Yoshikawa M. , Fujiwara A. , Kawaguchi J. ,   Hayabusa Mission & ScienceTeam
Published: May 2007

The spacecraft Hayabusa, which was launched in 2003, arrived at its destination, asteroid (25143) Itokawa in September 2005. The appearance of Itokawa, a small S-type near Earth asteroids, was totally unexpected. The surface is covered with a lot of boulders and there are only a few craters on it. It looks like a contact binary asteroid. The surface composition is quite similar to LL-chondrite. The estimated density is 1.9 ± 0.13 (g/cm3), so the macro-porosity is about 40%. This means that Itokawa is a rubble pile object. In Itokawa, we may see such things that are very close to building blocks of asteroids. In this paper, we review the mission and the first scientific results.
Asteroid mass determination with the Gaia mission
Authors: Mouret Serge , Hestroffer D. , Mignard F.
Published: May 2007

The main-belt asteroids are generally considered as the principal source for the near-Earth asteroids (NEAs). The ESA astrometric mission Gaia, due for launch in late 2011, will observe a very large number of asteroids (∼300,000 brighter than V = 20), the majority lying in the main-belt and with an unprecedented positional precision (at the sub-milliarcsecond level). Such high precision astrometry will enable to derive direct measures of the masses of the largest asteroids of which their precise determination will be of utmost significance for the knowledge of physical properties of asteroids. The method for computing the masses is based on the analysis of orbital perturbations during close encounters between massive asteroids (perturbers) and several smaller minor planets (targets). From given criteria of close approaches selection, we give the list of asteroids for which the mass can be determined, and the expected precision of these masses at mission completion.
Albedo and size of (99942) Apophis from polarimetric observations†
Authors: Cellino Alberto , Delbò Marco , Tedesco Edward F.
Published: May 2007

We have obtained the first accurate determination of the albedo of (99942) Apophis, by means of polarimetric observations carried out at the VLT. The observations allowed us to obtain the slope of the polarization–phase curve of this object, from which an albedo estimate of 0.33 ± 0.04 could be obtained. From our observations we also obtained a new estimate of the absolute magnitude:H= 19.7 ± 0.2 (assuming G=0.25, which applies to S- and Q-type asteroids). Based on these results, we derive for the size of Apophis a value of 270 ± 30 meters. The accuracy of this size estimate is mostly related to uncertainties inH, whereas the obtained albedo value should be considered more robust. Our observations convincingly show that polarimetry is an effective and efficient tool to obtain accurate albedos and sizes for small and faint potentially hazardous asteroids.
Concluding remarks: 15 years ago, now and in the near future
Authors: Milani Andrea
Published: May 2007

For conclusions, the traditional approach in IAU meetings is to have a highlights speech, in which the most important points of the meeting are stressed. After consulting with the co-chairs of the Scientific Organizing Committee, I decided I would rather discuss the spirit of this meeting from a more conceptual point of view.
Slip‐weakening distance estimated at near‐fault stations
Authors: Fukuyama Eiichi , Mikumo Takeshi
Published: April 2007

We estimated the slip‐weakening distance from the seismograms recorded at near‐fault stations, considering the effect of spatio‐temporal filtering for a continuous propagation of rupture. This effect is usually observed at some distance away from the fault. We used a Green's function for 2‐D anti‐plane rupture propagating with constant rupture velocity and instantaneous slip at the crack tip. As a source time function, we used a regularized Yoffe function which is a kinematically good approximation of dynamic slip‐weakening behavior. By convolving these functions, near‐fault waveforms are computed. As a proxy of slip‐weakening distance (Dc), we used Dc′, which is defined as a slip at the time of peak slip velocity. Then, Dc′ values can be computed as a function of the distance from the fault. This procedure is applied to the observation of the 2000 western Tottori, Japan, earthquake (MW6.6) as well as the 2002 Denali, Alaska, earthquake (MW7.9). We estimated Dc′ at about 0.3 m at GSH station (∼100 m away from the fault) for the Tottori earthquake and that at about 2.5 m at PS10 station (∼3 km away from the fault) for the Denali earthquake. We confirmed that both estimates are not affected by the spatio‐temporal smoothing.
How do the water vapor and carbon monoxide “tape recorders” start near the tropical tropopause?
Authors: Liu Chuntao , Zipser Ed , Garrett Tim , Jiang Jonathan H. , Su Hui
Published: May 2007

This paper evaluates geo‐seasonal relationships in tropical deep convection using radar and infrared data from Tropical Rainfall Measuring Mission (TRMM), near tropopause thin clouds from Stratospheric Air and Gas Experiment (SAGE) II, water vapor and carbon monoxide (CO) from the Earth Observing System (EOS) Microwave Limb Sounder (MLS), and the tropopause temperature from National Center of Environment Prediction (NCEP) reanalysis data. Geo‐seasonal variations in MLS water vapor at 146 hPa and 100 hPa are negatively correlated, which points to dehydration at the tropical tropopause. Water vapor at 146 hPa is highly correlated with tropical deep convection and thin clouds, but at 100 hPa it is more highly correlated with the tropopause temperature. There is a high correlation between the geo‐seasonal variations of 14–16 km thin cloud and cold clouds from deep convection. However, at 16–18 km, thin clouds are highly correlated with the tropopause temperature as well as with deep convection. There is a semi‐annual cycle in CO concentrations at 100 hPa and 146 hPa. The variability is consistent with the convolved seasonal variation of deep convection and surface biomass burning. The annual cycle of water vapor at 100 hPa correlates with the seasonal variability of “freezing and drying” between 146 hPa and 100 hPa, which in turn correlates with changes in tropopause temperature associated with deep convective lifting or large scale ascent.
Eddy transport of organic carbon and nutrients from the Chukchi Shelf: Impact on the upper halocline of the western Arctic Ocean
Authors: Mathis Jeremy T. , Pickart Robert S. , Hansell Dennis A. , Kadko David , Bates Nicholas R.
Published: May 2007

In September 2004 a detailed physical and chemical survey was conducted on an anticyclonic, cold‐core eddy located seaward of the Chukchi Shelf in the western Arctic Ocean. The eddy had a diameter of ∼16 km and was centered at a depth of ∼160 m between the 1000 and 1500 m isobaths over the continental slope. The water in the core of the eddy (total volume of 25 km3) was of Pacific origin, and contained elevated concentrations of nutrients, organic carbon, and suspended particles. The feature, which likely formed from the boundary current along the edge of the Chukchi Shelf, provides a mechanism for transport of carbon, oxygen, and nutrients directly into the upper halocline of the Canada Basin. Nutrient concentrations in the eddy core were elevated compared to waters of similar density in the deep Canada Basin: silicate (+20 μmol L−1), nitrate (+5 μmol L−1), and phosphate (+0.4 μmol L−1). Organic carbon in the eddy core was also elevated: POC (+3.8 μmol L−1) and DOC (+11 μmol L−1). From these observations, the eddy contained 1.25 × 109 moles Si, 4.5 × 108 moles NO3−, 5.5 × 107 moles PO3−, 1.2 × 108 moles POC, and 1.9 × 109 moles DOC, all available for transport to the interior of the Canada Basin. This suggests that such eddies likely play a significant role in maintaining the nutrient maxima observed in the upper halocline. Assuming that shelf‐to‐basin eddy transport is the dominant renewal mechanism for waters of the upper halocline, remineralization of the excess organic carbon transported into the interior would consume 6.70 × 1010 moles of O2, or one half the total oxygen consumption anticipated arising from all export processes impacting the upper halocline.
Downscaling of rain gauge time series by multiplicative beta cascade
Authors: Paulson Kevin S. , Baxter Paul D.
Published: May 2007

This paper develops a downscaling algorithm capable of producing ensembles of rain rate time series, with integration times as short as 10 s, consistent with a time series of rain rates with integration times as long as 6 hours. The algorithm is based on a stochastic multiplicative cascade using beta distributions as the random generator. The statistics of these cascades are developed in the paper. The cascade requires two parameters at each of a geometric progression of scales. These parameters are estimated from 1 gauge year of rain gauge data, with a 10 s integration period, collected in the southern United Kingdom. The statistical moments up to third order, of 9 gauge years of data, are calculated for integration times in the range 10 s to 6 hours. These data are compared with time series derived by accumulating 10 s data to larger integration times and then downscaling using the proposed algorithm. The proposed algorithm and parameters are expected to be applicable to downscaling 5 min or shorter rain rate data from temperate regions. For other regions, and longer initial accumulation times, some parameter estimation based on local data will be required.
Comparison of carbon monoxide measurements by TES and MOPITT: Influence of a priori data and instrument characteristics on nadir atmospheric species retrievals
Authors: Luo M. , Rinsland C. P. , Rodgers C. D. , Logan J. A. , Worden H. , Kulawik S. , Eldering A. , Goldman A. , Shephard M. W. , Gunson M. , Lampel M.
Published: May 2007

Comparisons of tropospheric carbon monoxide (CO) volume mixing ratio profiles and total columns are presented from nadir‐viewing measurements made by the Tropospheric Emission Spectrometer (TES) on the NASA Aura satellite and by the Measurements of Pollution in the Troposphere (MOPITT) instrument on the NASA Terra satellite. In this paper, we first explore the factors that relate the retrieved and the true species profiles. We demonstrate that at a given location and time the retrieved species profiles reported by different satellite instrument teams can be very different from each other. We demonstrate the influence of the a priori data and instrument characteristics on the CO products from TES and MOPITT and on their comparisons. Direct comparison of TES and MOPITT retrieved CO profiles and columns show significant differences in the lower and upper troposphere. To perform a more proper and rigorous comparison between the two instrument observations we allow for different a priori profiles and averaging kernels. We compare (1) TES retrieved CO profiles adjusted to the MOPITT a priori with the MOPITT retrievals and (2) the above adjusted TES CO profiles with the MOPITT profiles vertically smoothed by the TES averaging kernels. These two steps greatly improve the agreement between the CO profiles and the columns from the two instruments. No systematic differences are found as a function of latitude in the final comparisons. These results show that knowledge of the a priori profiles, the averaging kernels, and the error covariance matrices in the standard data products provided by the instrument teams and understanding their roles in the retrieval products are essential in quantitatively interpreting both retrieved profiles and the derived total or partial columns for scientific applications.
On the global distribution, seasonality, and budget of atmospheric carbonyl sulfide (COS) and some similarities to CO2
Authors: Montzka S. A. , Calvert P. , Hall B. D. , Elkins J. W. , Conway T. J. , Tans P. P. , Sweeney C.
Published: May 2007

Measurements of carbonyl sulfide (COS) from a global air‐monitoring network over multiple years suggest that atmospheric mixing ratios of COS are strongly influenced by terrestrial vegetation in the Northern Hemisphere (NH) and by the oceans in the Southern Hemisphere (SH). The annual mean NH mixing ratio estimated from results at seven surface sites during 2000.2–2005.2 was 476 ± 4 ppt, or slightly less than the mean of 491 ± 2 ppt derived from results at three surface sites in the SH. The lowest annual mean mixing ratios were measured at low‐altitude continental sites in the midlatitude and high‐latitude NH. Mixing ratios undergo substantial seasonal variations at nearly all sites across the globe; the largest seasonal variations are observed at the NH sites having the lowest annual means. There is little coherence in the seasonality in the NH and SH, suggesting that the COS seasonality is driven by different processes in each hemisphere. These seasonal changes cause the NH/SH ratio, as estimated from the available surface data, to vary regularly from 0.91 ± 0.01 to 1.04 ± 0.02 across a year; the annual mean NH/SH ratio was 0.97 ± 0.01. Results from over 160 aircraft profiles regularly collected at eight sites over the continental United States throughout an entire year reveal substantial vertical gradients for COS mixing ratios that vary with season. While similar mixing ratios are observed throughout the NH troposphere during January–April (up to 8 km above sea level (asl)), during the growing season substantially reduced mixing ratios are observed in the boundary layer above the continental United States (defined here as <2 km asl). The surface and aircraft results for COS show strong similarities to atmospheric CO2, though both the amplitude of seasonal variations measured at Earth's surface and the observed vertical gradients during the growing season are 5–6 times larger for COS than for CO2 on a relative basis. A qualitative analysis of the results in light of known sources and sinks suggests (1) that terrestrial uptake, most likely due to photosynthetically active vegetation, dominates the seasonality observed throughout the Northern Hemisphere at a rate that is about 5 times greater than estimates based upon scaling net primary production by mean, ambient air mixing ratios of COS to CO2, (2) the oceans dominate the seasonality observed in the Southern Hemisphere, and (3) biomass burning has a small influence on the seasonality observed for COS in the extratropics of both hemispheres.
Meteorological conditions and anomalies during the Intercontinental Chemical Transport Experiment–North America
Authors: Fuelberg Henry E. , Porter Michael J. , Kiley Christopher M. , Halland Jeremy J. , Morse Danielle
Published: May 2007

Meteorological conditions are described during the Intercontinental Chemical Transport Experiment–North America (INTEX‐NA) that was conducted over the United States during July and August 2004. Relatively zonal flow dominated the contiguous United States during the first 2 weeks of the mission, while a series of large amplitude troughs traversed the eastern half of the country during the final 4 weeks. These troughs were accompanied by cold fronts reaching the Gulf of Mexico, an uncommon occurrence during August. Frontal passages over the northeast were somewhat above average, but the short time interval between passages precluded the formation of stagnant high‐pressure centers containing abundant pollution. Atmospheric chemistry during INTEX‐NA was heavily influenced by record‐breaking fires over Alaska and western Canada. Persistent high pressure over Alaska provided ideal conditions for the wildfires and for transporting their burning by‐products southeastward toward the INTEX domain where they were sampled frequently by INTEX aircraft. Forward trajectories and satellite imagery showed that the plumes later were carried to parts of Europe, Africa, and even the Arctic. Deep convection and lightning were important factors during INTEX‐NA. Cloud‐to‐ground (CG) lightning data show that horizontal patterns and numbers of lightning flashes during INTEX‐NA are similar to those of 2003 and 2005. Statistics derived from 10 day backward trajectories indicate that the DC‐8 often sampled lightning influenced air.
Hydrogen peroxide, methyl hydroperoxide, and formaldehyde over North America and the North Atlantic
Authors: Snow Julie A. , Heikes Brian G. , Shen Haiwei , O'Sullivan Daniel W. , Fried Alan , Walega Jim
Published: May 2007

Hydrogen peroxide (H2O2), methyl hydroperoxide (CH3OOH), and formaldehyde (CH2O) were measured over North America and the North Atlantic during the INTEX‐NA, TOPSE, and SONEX aircraft campaigns. An overview of H2O2, CH3OOH, and CH2O across the geographic and temporal range of these campaigns is presented. H2O2, CH3OOH, and CH2O mixing ratios and variability were larger during INTEX‐NA compared to TOPSE and SONEX. Mean H2O2, CH3OOH, and CH2O were 1390, 440, and 480 pptv, respectively, more than two times higher than TOPSE measurements and an order of magnitude higher than SONEX measurements. This is attributed to higher solar radiation levels and the more polluted conditions of INTEX‐NA. Mixing ratios and variability decreased with altitude for all three gases and on all three campaigns, except for CH3OOH during TOPSE. The impact of convection on H2O2, CH3OOH, and CH2O is also discussed. Using the ratio H2O2/CH3OOH, convectively influenced air parcels were found to be enhanced in CH3OOH, CH2O, CO, NO, and NO2 while H2O2 and HNO3 were depleted by wet removal. Biomass burning was also shown to increase H2O2, CH3OOH, and CH2O mixing ratios up to 1.5, 2, and 1 ppbv, respectively, even after 4–5 days of transit. Results from this study show considerable variability in H2O2, CH3OOH, and CH2O throughout the North American and North Atlantic troposphere. The variability in the upper troposphere is driven by local photochemical production and transport via regional convection and long‐range pathways, suggesting transport mechanisms are important factors to include in photochemical models simulating H2O2, CH3OOH, CH2O, and HOx.
Impacts of vegetation and cold season processes on soil moisture and climate relationships over Eurasia
Authors: Dong Jiarui , Ni‐Meister Wenge , Houser Paul R.
Published: May 2007

A number of modeling studies have addressed soil moisture persistence and its effects on the atmosphere. Such analyses are particularly valuable for seasonal to interannual prediction. In this study, we perform an observation‐based study to further investigate the impacts of vegetation and cold season processes on soil moisture persistence and climate feedbacks. The joint analysis of independent meteorological, soil moisture and land cover measurements, without the use of a model, in the former Soviet Union provides a unique look at soil moisture–climate relationships at seasonal to interannual timescales. Averaged data over the growing season show a strong consistency between soil moisture and precipitation over grassland dominant regions, suggesting that precipitation anomalies are a dominant control of soil moisture at interannual timescales. Investigation of soil moisture persistence at the seasonal timescale shows a strong correlation between soil moisture in spring and the subsequent precipitation in summer over forest dominant regions and between cold season precipitation accumulation in winter and soil moisture in the following spring. Our findings can be explained by the theory proposed by Koster and Suarez (2001) and are consistent with the results from other modeling studies. Although it is hard to obtain the statistical meaningful conclusions because of the short data records, our results show the potential role of vegetation and cold season processes in land‐atmosphere interactions. Further modeling studies and analyses using long in situ data records are necessary to fully verify our results.
Evolution of lakes and basins in northern Alaska and discussion of the thaw lake cycle
Authors: Jorgenson M. Torre , Shur Yuri
Published: May 2007

We evaluated the development of lake basins on the central coastal plain of northern Alaska on the basis of topographic profiles, soil and ground ice surveys, radiocarbon dating, photogrammetric analysis, and regional comparisons. Our analysis reveals that lake evolution is much more complex and less cyclic than theorized by previous investigations. In the area we studied, there was insufficient ground ice in the oldest terrain to form thaw lakes, the aggradation of ice in the margins of drained lake basins was insufficient to heave the surface up to near original topographic conditions, and the process occurs at too slow a rate for a “thaw lake cycle” to develop within the Holocene. Accordingly, we revised the conceptual model of lake and basin development to be consistent with the patterns and process we observed on the extensive sand sheets underlying most of the coastal plain. Developmental stages include (1) initial flooding of depressions to form primary lakes, (2) lateral erosion, with sorting and redistribution of sediments, (3) lake drainage as the stream network expands, (4) differential ice aggradation in silty centers and sandy margins, (5) formation of secondary thaw lakes in the heaved centers of ice‐rich basins and infilling of ponds along the low margins, and (6) basin stabilization.
Groundwater and soil chemical changes under phreatophytic tree plantations
Authors: Jobbágy Esteban G. , Jackson Robert B.
Published: May 2007

The onset of groundwater consumption by plants can initiate a pathway of chemical inputs from aquifers to ecosystems, typically absent in groundwater recharge areas. We explored this biogeochemical transfer and its influence on soils in phreatophytic eucalypt plantations and native grasslands of the Pampas (Argentina). Groundwater and soil chemical observations at three grassland/plantation pairs were complemented with more detailed analyses along a 400‐m‐long grassland‐plantation transect. Although tree plantations showed a widespread and homogeneous salinization of groundwater and soils at all study sites, chemical contrasts between the plantation edge and core were evident along the study transect. Nonsalty, slightly acidic, bicarbonate‐dominated waters in the grassland changed sharply within the plantation, with dissolved chloride, sulfate, calcium, and magnesium peaking at the plantation core (200 m away from the grassland) and dissolved sodium, carbonate, bicarbonate, and pH peaking toward the edge (0–50 m away from the grassland) and declining toward the core. In agreement with these differences, soil alkalinization was the strongest at the plantation edge but absent in the core. Groundwater flow simulations using FLOWNET suggested trajectories of increasing length and depth and older groundwater ages (confirmed by tritium analyses) toward the plantation core, explaining the hydrochemical contrasts within the plantation. Flow simulations and chloride mass balances suggested discharges of 250–500 mm yr−1to the plantations. In our sites phreatophytic discharge controlled solute transfers from groundwater through (1) altered flow within the aquifer, affecting solute transport to the rooting zone, and (2) water uptake plus solute exclusion, concentrating solutes in the rooting zone. While the first mechanism may be restricted to the core of large phreatophytic areas, the second is likely to occur more generally in phreatophytic ecosystems.
Holocene climate variability in the western Mediterranean region from a deepwater sediment record
Authors: Frigola J. , Moreno A. , Cacho I. , Canals M. , Sierro F. J. , Flores J. A. , Grimalt J. O. , Hodell D. A. , Curtis J. H.
Published: May 2007

The detailed analysis of the International Marine Past Global Changes Study core MD99‐2343 recovered from a sediment drift at 2391 m water depth north of the island of Minorca illustrates the effects of climate variability on thermohaline circulation in the western Mediterranean during the last 12 kyr. Geochemical ratios associated with terrigenous input resulted in the identification of four phases representing different climatic and deepwater overturning conditions in the Western Mediterranean Basin during the Holocene. Superimposed on the general trend, eight centennial‐ to millennial‐scale abrupt events appear consistently in both grain size and geochemical records, which supports the occurrence of episodes of deepwater overturning reinforcement in the Western Mediterranean Basin. The observed periodicity for these abrupt events is in agreement with the previously defined Holocene cooling events of the North Atlantic region, thus supporting a strong Atlantic‐Mediterranean climatic link at high‐frequency time intervals during the last 12 kyr. The rapid response of the Mediterranean thermohaline circulation to climate change in the North Atlantic stresses the importance of atmospheric teleconnections in transferring climate variability from high latitudes to midlatitudes.
Applicability criteria of the variable parameter Muskingum stage and discharge routing methods
Authors: Perumal Muthiah , Sahoo Bhabagrahi
Published: May 2007

The applicability criteria of the variable parameter Muskingum stage hydrograph (VPMS) and the variable parameter Muskingum discharge hydrograph (VPMD) routing methods are assessed and quantified. The assessment is made by studying the propagation characteristics of hypothetical stage hydrographs of the form of a four parameter Pearson type III distribution and its corresponding discharge hydrographs in uniform rectangular and trapezoidal channels using the VPMS and the VPMD methods, respectively, in comparison with the propagation characteristics of the respective hydrographs simulated by solving the Saint‐Venant equations, which form the benchmark model. For each of the uniform rectangular and trapezoidal shape channel categories, a total of 2880 numerical experiments covering various combinations of Manning's roughness coefficient, channel bed slope, peak stage and respective time to peak, and shape factors of the stage hydrographs were conducted for each of these VPMS and VPMD methods, respectively, by routing the hypothetical stage and the respective discharge hydrographs for a reach length of 40 km. The routed stage and discharge hydrographs were compared with the corresponding Saint‐Venant solutions using four performance measures, namely, percentage variance explained, percentage error in volume, percentage error in peak, and percentage error in time to peak. Considering a maximum error of 5% of these measures, the experiments indicate that the applicability limit of the VPMS method for stage routing is (1/So)(∂y/∂x)max ≤ 0.79, while for the simultaneous computation of the discharge hydrograph corresponding to the routed stage hydrograph this method can be applied up to (1/So)(∂y/∂x)max ≤ 0.63 (where So is the channel slope and ∂y/∂x is the water profile gradient). The VPMD method is applicable up to (1/So)(∂y/∂x)max ≤ 0.43 for both discharge routing and the corresponding stage computation. The applicability of the VPMD method is compared with the variable parameter Muskingum‐Cunge (VPMC) method, an alternative method for discharge hydrograph routing, and it is found that for the same 5% error criteria of the VPMD method, the VPMC method is applicable only up to (1/So)(∂y/∂x)max ≤ 0.11. Thus it is seen that the VPMD method has an improved performance and wider applicability range than the VPMC method.
Impact of Saharan air layer on hurricane peak intensity
Authors: Wu Liguang
Published: May 2007

The Saharan air layer (SAL), which is associated with African dust outbreaks, forms as air moves across the Sahara Desert, containing substantial amounts of mineral dust. While the relationships of Sahel rainfall with African dust outbreaks and Atlantic hurricane activity have been documented in previous studies, analyses of various independent datasets show that the Sahel rainfall, SAL activity and hurricane peak intensity in the Atlantic basin are highly correlated. The long‐term trend in hurricane peak intensity generally follows the Sahel rainfall and SAL activity. The decreasing trend in hurricane intensity by the mid‐1980s was associated with the enhancing SAL activity (drying relative humidity and enhancing vertical shear) and the severe drought in the Sahel, while the recent moderate increasing trend in hurricane intensity is consistent with the weakening SAL activity (wetting relative humidity, weakening vertical shear and decreasing dust load) and the ameliorating Sahel drought. This study suggests that the SAL may act as a link between the summer African monsoon and Atlantic hurricane activity.
Interannual variations of tropical instability waves observed by the Tropical Rainfall Measuring Mission
Authors: Wu Qiaoyan , Bowman Kenneth P.
Published: May 2007

Eight years of microwave data from the Tropical Rainfall Measuring Mission (TRMM) satellite are used to study the interannual variations of tropical instability waves (TIWs) in the Pacific and Atlantic Oceans. SST signatures of TIWs in the Pacific Ocean are strongest during the cold phase of ENSO, when the cold tongue is most pronounced. The waves are weak during the warm phase of ENSO. A low‐frequency Atlantic air‐sea coupled equatorial mode affects TIW activity in the Atlantic in a similar fashion. Interannual variations in sea‐surface temperatures due to TIW activity can produce interannual variations in the atmospheric mesoscale response.
Signalling mechanisms in skeletal muscle: role in substrate selection and muscle adaptation
Authors: Hawley John A. , Hargreaves Mark , Zierath Juleen R.
Published: May 2007

Exercise produces a multitude of time- and intensity-dependent physiological, biochemical and molecular changes within skeletal muscle. With the onset of contractile activity, cytosolic and mitochondrial [Ca2+] levels are rapidly increased and, depending on the relative intensity of the exercise, metabolite concentrations change (i.e. increases in [ADP] and [AMP], decreases in muscle creatine phosphate and glycogen). These contraction-induced metabolic disturbances activate several key kinases and phosphatases involved in signal transduction. Important among these are the calcium dependent signalling pathways that respond to elevated Ca2+ concentrations (including Ca2+/calmodulin-dependent kinase, Ca2+-dependent protein kinase C and the Ca2+/calmodulin-dependent phosphatase calcineurin), the 5′-adenosine monophosphate-activated protein kinase, several of the mitogen-activated protein kinases and protein kinase B/Akt. The role of these signal transducers in the regulation of carbohydrate and fat metabolism in response to increased contractile activity has been the focus of intense research efforts during the past decade.
Fatty acid metabolism in adipose tissue, muscle and liver in health and disease
Authors: Frayn Keith N. , Arner Peter , Yki-Järvinen Hannele
Published: May 2007

Fat is the largest energy reserve in mammals. Most tissues are involved in fatty acid metabolism, but three are quantitatively more important than others: adipose tissue, skeletal muscle and liver. Each of these tissues has a store of triacylglycerol that can be hydrolysed (mobilized) in a regulated way to release fatty acids. In the case of adipose tissue, these fatty acids may be released into the circulation for delivery to other tissues, whereas in muscle they are a substrate for oxidation and in liver they are a substrate for re-esterification within the endoplasmic reticulum to make triacylglycerol that will be secreted as very-low-density lipoprotein. These pathways are regulated, most clearly in the case of adipose tissue. Adipose tissue fat storage is stimulated, and fat mobilization suppressed, by insulin, leading to a drive to store energy in the fed state. Muscle fatty acid metabolism is more sensitive to physical activity, during which fatty acid utilization from extracellular and intracellular sources may increase enormously. The uptake of fat by the liver seems to depend mainly upon delivery in the plasma, but the secretion of very-low-density lipoprotein triacylglycerol is suppressed by insulin. There is clearly cooperation amongst the tissues, so that, for instance, adipose tissue fat mobilization increases to meet the demands of skeletal muscle during exercise. When triacylglycerol accumulates excessively in skeletal muscle and liver, sometimes called ectopic fat deposition, then the condition of insulin resistance arises. This may reflect a lack of exercise and an excess of fat intake.
The anti-inflammatory effect of exercise: its role in diabetes and cardiovascular disease control
Authors: Pedersen Bente Klarlund
Published: May 2007

Chronic low-grade systemic inflammation is a feature of chronic diseases such as cardiovascular disease and type 2 diabetes. Regular exercise offers protection against all-cause mortality, primarily by protection against atherosclerosis and insulin resistance and there is evidence that physical training is effective as a treatment in patients with chronic heart diseases and type 2 diabetes.

Regular exercise induces anti-inflammatory actions. During exercise, IL-6 (interleukin-6) is produced by muscle fibres. IL-6 stimulates the appearance in the circulation of other anti-inflammatory cytokines such as IL-1ra (interleukin-1 receptor antagonist) and IL-10 (interleukin-10) and inhibits the production of the pro-inflammatory cytokine TNF-a (tumour necrosis factor-a). In addition, IL-6 enhances lipid turnover, stimulating lipolysis as well as fat oxidation. It is suggested that regular exercise induces suppression of TNF-a and thereby offers protection against TNF-a-induced insulin resistance. Recently, IL-6 was introduced as the first myokine, defined as a cytokine, that is produced and released by contracting skeletal muscle fibres, exerting its effects in other organs of the body. Myokines may be involved in mediating the beneficial health effects against chronic diseases associated with low-grade inflammation such as diabetes and cardiovascular diseases.
Vascular nitric oxide: effects of physical activity, -importance for health
Authors: McAllister Richard M. , Laughlin M. Harold
Published: May 2007

NO (nitric oxide), formed in the vascular endothelium and derived from a biochemical reaction catalysed by eNOS (endothelial NO synthase), appears to play a role in exercise-induced dilation of blood vessels supplying cardiac and skeletal muscle. Endothelium-dependent, NO-mediated vasodilation is augmented by exercise training. Increases in eNOS gene transcription, eNOS mRNA stability and eNOS protein translation appear to contribute to increased NO formation and, consequently, enhanced NO-mediated vasodilation after training. Enhanced endothelial NO formation may also have a role(s) in the prevention and management of atherosclerosis because several steps in the atherosclerotic disease process are inhibited by NO. A growing body of work suggests that exercise training, perhaps via increased capacity for NO formation, retards atherosclerosis. This has significant implications for human health, given that atherosclerosis is the leading killer in Western society.
Vascular function in the metabolic syndrome and the effects on skeletal muscle perfusion: lessons from the obese Zucker rat
Authors: Frisbee Jefferson C. , Delp Michael D.
Published: May 2007

The increased prevalence of obesity in Western society has been well established for many years, and with this trend, the prevalence of other associated pathologies including insulin resistance, dyslipidaemia, hypertension and the genesis of a proinflammatory and prothrombotic environment within individuals is also rapidly increasing, resulting in a condition known as the~metabolic syndrome. From a physiological perspective, one of the most severe consequences of the metabolic syndrome is a progressive inability of the cardiovascular system to adequately perfuse tissues and organs during either elevated metabolic demand and, if sufficiently severe, under basal levels of demand. For the study of the metabolic syndrome, the OZR (obese Zucker rat) represents an important tool in this effort, as the metabolic syndrome in these animals results from a chronic hyperphagia, and thus can be an excellent representation of the human condition. As in afflicted humans, OZR experience an attenuated functional and reactive hyperaemia, and can ultimately experience an ischaemic condition in their skeletal muscles at rest. The source of this progressive ischaemia appears to lie at multiple sites, as endothelium-dependent vasodilator responses are strongly impaired in OZR, and specific constrictor processes (e.g. adrenergic tone) may be enhanced. Whilst these active processes may contribute to a reduction in blood flow under resting conditions or with mild elevations in metabolic demand, an evolving structural alteration to individual microvessels (reduced distensibility) and microvascular networks (reduced microvessel density) also develop and may act to constrain perfusion at higher levels of metabolic demand. Given that constrained muscle perfusion in the metabolic syndrome appears to reflect a highly integrated, multi-faceted effect in OZR, and probably in humans as well, therapeutic interventions must be designed to address each of these contributing elements.
An increase in plasma adiponectin multimeric complexes follows hypocaloric diet-induced weight loss in obese and overweight pre-menopausal women
Authors: Polak Jan , Kovacova Zuzana , Jacek Martin , Klimcakova Eva , Kovacikova Michaela , Vitkova Michaela , Kuda Ondrej , Sebela Marek , Samcova Eva , Stich Vladimir
Published: May 2007

Adiponectin is involved in the regulation of glucose and fatty acid metabolism, influences whole-body insulin sensitivity and protects arterial walls against the development of atherosclerosis. Plasma adiponectin is decreased in obese, insulin-resistant and Type 2 diabetic patients. Adiponectin circulates in plasma as high-, medium- and low-molecular-weight (‘mass’) forms (HMW, MMW and LMW respectively). The HMW form is believed to be closely associated with insulin sensitivity. The aim of the present study was to investigate whether diet-induced changes in body weight and insulin sensitivity were associated with changes in the quantity of adiponectin multimeric complexes. A total of 20 overweight or obese women (age, 39.4±9.5 years; body mass index, 32.2±6.4 kg/m2) underwent 12 weeks of low caloric diet (600 kcal/day less than energy requirements; where 1 kcal≈4.184 kJ). Plasma samples were drawn before and after the study for biochemical analysis and Western blot detection of adiponectin multimeric complexes. The hypocaloric diet resulted in a weight reduction (89.8±16.4 kg compared with 83.1±15.6 kg; P<0.001) and an improvement in whole-body insulin sensitivity, as measured by HOMA (homoeostasis model assessment index; 1.9±0.8 compared with 1.5±0.7; P=0.013). Increases in the quantities of the HMW, MMW and LMW forms by 5.5, 8.5 and 18.1% respectively, were observed (P<0.05 for all of the forms). Total plasma adiponectin was increased by 36% with borderline significance (P=0.08). No correlations between changes in adiponectin complexes and changes in indices of insulin sensitivity were observed. In conclusion, diet-induced weight loss improved insulin sensitivity as well as increased the amount of HMW, MMW and LMW adiponectin complexes in plasma.
Measurement of Intelligibility in Disordered Speech
Authors: Klein Edward S. , Flint Cari B.
Published: May 2007

Purpose

To determine empirically which of three frequently observed rules in children with phonological disorders contributes most to difficulties in speaker intelligibility.

Method

To evaluate the relative effects on intelligibility of deletion of final consonants (DFC), stopping of fricatives and affricates (SFA), and fronting of velars (FV), phonologically reduced sentences were read to groups of adult listeners at normal levels of occurrence for typical conversation and at equal levels of occurrence.

Results

DFC had a greater effect than SFA on intelligibility, which had a greater effect than FV on intelligibility, when these rules occurred at levels approximating those seen in typical conversational speech. Results differed, however, when opportunities for rule occurrence were equalized. At relatively low levels of occurrence, FV had less effect on intelligibility than did SFA and DFC, but no significant differences in intelligibility were found between the latter two rules. At relatively high levels of occurrence, no significant differences between the three rules were observed.

Implications

These findings may be important clinically for clinicians who are trying to determine which rules should be targeted first in therapy.
Evidence-Based Practice: An Examination of Its Ramifications for the Practice of Speech-Language Pathology
Authors: Ratner Nan Bernstein
Published: May 2007

Purpose

The purpose of this article is to consider some of the ramifications that arise when a discipline newly endorses evidence-based practice (EBP) as a primary guiding principle. Although EBP may appear straightforward, events experienced by peer disciplines that have preceded us in the implementation of EBP raise questions about defining acceptable forms of evidence for treatment effectiveness and efficacy, the potential roles of nonspecific or common factors, therapist quality in achieving therapy outcomes, and eventual applications of EBP that may overly confine which treatments are considered acceptable and reimbursable.

Method

Through narrative review of the literature, the article examines valuable as well as controversial features of EBP in addition to obstacles that may impede the transition of evidence (research findings) to clinical practice.

Conclusion

EBP is a valuable construct in ensuring quality of care. However, bridging between research evidence and clinical practice may require us to confront potentially difficult issues and establish thoughtful dialogue about best practices in fostering EBP itself.