bluuebunny/crossref_metadata_2025 huggingface dataset:
Satellite observations of aerosol transport from East Asia to the Arctic: three case studies
Authors: Di Pierro M. , Jaeglé L. , Anderson T. L.
Published: March 2011

Abstract. Vertical profiles of aerosol extinction obtained with the CALIOP lidar onboard CALIPSO are used in conjunction with the GEOS-Chem chemical transport model and NOAA's HYSPLIT trajectory model to document three aerosol export events from East Asia to the Arctic in the year 2007. During each of these events CALIOP sampled the pollution plumes multiple times over periods of five to seven days. Midlatitude cyclones lifted the pollution to the free troposphere with net diabatic heating of ~5 °C day−1 and precipitation in this initial ascending stage. Rapid meridional transport to the Arctic took place at 3–7 km altitude, and was mediated by either a blocking high pressure system in the NW Pacific or a trough-ridge configuration. Once in the Arctic transport was nearly isentropic with slow subsidence and radiative cooling at a rate of 1–1.5 °C day−1. We find good agreement between modeled and observed plumes in terms of length, altitude, thickness and, within the measurement uncertainties, extinction coefficient. In one event the satellite algorithm misclassifies the aerosol layer as ice clouds as a result of the relatively high depolarization ratio (0.06), likely caused by a high dust component in the aerosol mixture. Using 500 hPa geopotential height anomalies for these three events along with eight other export events observed by CALIOP in 2007–2009, we develop a meteorological index that captures 40–60% of the variance of Asian transport events to the Arctic in winter and spring. Simulations with the GEOS-Chem model show that 6 major export events from Asia to the Arctic occur each year, on average. The maximum probability for such events is during March–June, with a secondary maximum in October–November. During these events, Asian pollution and dust aerosols account for 50–70% of the aerosol optical depth over the Siberian sector of the Arctic, compared to a mean background contribution of 33%.
Evaluation of satellite-derived HCHO using statistical methods
Authors: Kim J. H. , Kim S. M. , Baek K. H. , Wang L. , Kurosu T. , De Smedt I. , Chance K. , Newchurch M. J.
Published: March 2011

Abstract. Most previous evaluations of satellite performance relied on pair wise comparisons with limited spatial and temporal coverage of surface-based measurements such as soundings and in-situ measurements. Especially, validation of satellite HCHO measurements is very difficult because ground-based HCHO measurements are extremely sparse. We use a new scientific approach, statistical analyses with empirical orthogonal function (EOF) and singular value decomposition (SVD), to provide three-dimensional results of comparisons with a global picture over long measurement periods. The EOF and SVD analyses with GOME, SCIAMACHY and OMI HCHO, and MOPITT CO show dipole distributions oscillating between northern and southern equatorial Africa with an annual cycle. This feature is exactly coincident with the spatial and temporal pattern of biomass burning occurring over tropical Africa. The double-peaked maximum seen in OMI HCHO is only marginally observed in SCIAMACHY and GOME HCHO seasonality over the northern tropical region during northern biomass-burning season. Spatial and temporal difference between two datasets may cause this discrepancy, but the detailed analysis for the cause requires an examination with a chemical model. The statistical analyses of all data indicate that biomass-burning activity over South America is responsible for the HCHO seasonality over that continent. We have not observed any evidence to support the influence of biogenic activity on HCHO over these regions; however, we find robust evidence that biomass burning is the strongest source of HCHO over tropical Africa and South America. We also found that these statistical tools are a very efficient method for evaluating satellite data.
Ice nucleation from aqueous NaCl droplets with and without marine diatoms
Authors: Alpert P. A. , Aller J. Y. , Knopf D. A.
Published: March 2011

Abstract. Ice formation in the atmosphere by homogeneous and heterogeneous nucleation is one of the least understood processes in cloud microphysics and climate. Here we describe our investigation of the marine environment as a potential source of atmospheric IN by experimentally observing homogeneous ice nucleation from aqueous NaCl droplets and comparing against heterogeneous ice nucleation from aqueous NaCl droplets containing intact and fragmented diatoms. Homogeneous and heterogeneous ice nucleation are studied as a function of temperature and water activity, aw. Additional analyses are presented on the dependence of diatom surface area and aqueous volume on heterogeneous freezing temperatures, ice nucleation rates, ωhet, ice nucleation rate coefficients, Jhet, and differential and cumulative ice nuclei spectra, k(T) and K(T), respectively. Homogeneous freezing temperatures and corresponding nucleation rate coefficients are in agreement with the water activity based homogeneous ice nucleation theory within experimental and predictive uncertainties. Our results confirm, as predicted by classical nucleation theory, that a stochastic interpretation can be used to describe this nucleation process. Heterogeneous ice nucleation initiated by intact and fragmented diatoms can be adequately represented by a modified water activity based ice nucleation theory. A horizontal shift in water activity, Δaw, het = 0.2303, of the ice melting curve can describe median heterogeneous freezing temperatures. Individual freezing temperatures showed no dependence on available diatom surface area and aqueous volume. Determined at median diatom freezing temperatures for aw from 0.8 to 0.99, ωhet ~ 0.11+0.06−0.05 s−1, Jhet ~ 1.0+1.16−0.61 × 104 cm−2 s−1, and K ~ 6.2+3.5−4.1 × 104 cm−2. The experimentally derived ice nucleation rates and nuclei spectra allow us to estimate ice particle production which we subsequently use for a comparison with observed ice crystal concentrations typically found in cirrus and polar marine mixed-phase clouds. Differences in application of time-dependent and time-independent analyses to predict ice particle production are discussed.
Coupled vs. decoupled boundary layers in VOCALS-REx
Authors: Jones C. R. , Bretherton C. S. , Leon D.
Published: March 2011

Abstract. We analyze the extent of subtropical stratocumulus-capped boundary layer decoupling and its relation to other boundary-layer characteristics and forcings using aircraft observations from VOCALS-REx along a swath of the subtropical southeast Pacific Ocean running west 1600 km from the coast of Northern Chile. We develop two complementary and consistent measures of decoupling. The first is based on boundary layer moisture stratification in flight profiles from near the surface to above the capping inversion, and the second is based the difference between the lifted condensation level (LCL) and a mean lidar-derived cloud base measured on flight legs at 150m altitude. Most flights took place during early-mid morning, well before the peak in insolation-induced decoupling. We find that the boundary layer is typically shallower, drier, and well mixed near the shore, and tends to deepen, decouple, and produce more drizzle further offshore to the west. Decoupling is strongly correlated to the “well-mixed cloud thickness”, defined as the difference between the capping inversion height and the LCL; other factors such as wind speed, cloud droplet concentration, and inversion thermodynamic jumps have little additional explanatory power. The results are broadly consistent with the deepening-warming theory of decoupling. In the deeper boundary layers observed well offshore, there was frequently nearly 100% boundary-layer cloud cover despite pronounced decoupling. The cloud cover was more strongly correlated to a κ parameter related to the inversion jumps of humidity and temperature, though the exact functional relation is slightly different than found in prior large-eddy simulation studies.
The kinetics and mechanism of an aqueous phase isoprene reaction with hydroxy radical
Authors: Huang D. , Zhang X. , Chen Z. M. , Zhao Y. , Shen X. L.
Published: March 2011

Abstract. Aqueous phase chemical processes of organic compounds in the atmosphere have received increasing attention, partly due to their potential contribution to the formation of secondary organic aerosol (SOA). Here, we analyzed the aqueous oxidation of isoprene in clouds and its reaction products, including carbonyl compounds and organic acids. We also performed a laboratory simulation to improve our understanding of the kinetics and mechanisms for the products of aqueous isoprene oxidation that are significant precursors of SOA; these included methacrolein (MACR), methyl vinyl ketone (MVK), methyl glyoxal (MG), and glyoxal (GL). We used a novel chemical titration method to monitor the concentration of isoprene in the aqueous phase. We used a box model to interpret the mechanistic differences between aqueous- and gas-phase OH radical-initiated isoprene oxidations. Our results were the first demonstration of the rate constant for the reaction between isoprene and OH radical in water, 3.50 (± 0.98) × 109 M−1 s−1 at 283 K. Molar yields were determined based on consumed isoprene. Of note, the ratio of the yields of MVK (18.9 ± 0.8%) to MACR (9.0 ± 1.1%) in the aqueous phase isoprene oxidation was approximately double that observed for the corresponding gas phase reaction. We hypothesized that this might be explained by a water-induced enhancement in the self-reaction of a hydroxy isoprene peroxyl radical (HOCH2C(CH3)(O2)CH = CH2) produced in the aqueous reaction. The observed yields for MG and GL were 11.4 ± 0.3% and 3.8 ± 0.1%, respectively. Model simulations indicated that several potential pathways may contribute to the formation of MG and GL. Finally, oxalic acid increased steadily throughout the course of the study, even after isoprene was consumed completely. The observed yield of oxalic acid was 26.2 ± 0.8% at 6 h. The observed carbon balance accounted for ~50% of the consumed isoprene. The presence of high-molecular-weight compounds may have accounted for a large portion of the missing carbons, but they were not quantified in this study. In summary, our work has provided experimental evidence that condensed water could affect the distribution of oxygenated organic compounds produced in the oxidation of volatile organic compounds. If volatile organic compounds like isoprene and terpenes undergo aqueous oxidation to a larger extent than considered previously, the contribution of their atmospheric aqueous oxidation should be considered when constructing future models of the global SOA budget.
VOC reactivity and its effect on ozone production during the HaChi summer campaign
Authors: Ran L. , Zhao C. S. , Xu W. Y. , Lu X. Q. , Han M. , Lin W. L. , Yan P. , Xu X. B. , Deng Z. Z. , Ma N. , Liu P. F. , Yu J. , Liang W. D. , Chen L. L.
Published: March 2011

Abstract. Measurements of ozone and its precursors conducted within the HaChi (Haze in China) project in summer 2009 were analyzed to characterize volatile organic compounds (VOCs) and their effects on ozone photochemical production at a suburban site in the North China Plain. Ozone episodes, during which running 8-h average ozone concentrations exceeding 80 ppbv lasted for more than 4 h, occurred on about two thirds of the observational days during the 5-week field campaign. This suggests continuous ozone exposure risks in this region during the summer. The average concentrations of nitrogen oxides (NOx) and VOCs are about 20 ppbv and 650 ppbC, respectively. Total VOC reactivity is dominated by anthropogenic VOCs, including aromatics, alkanes and most alkenes. The contribution of biogenic VOCs to total ozone-forming potential, however, is also considerable in the daytime. 2-butenes, isoprene, trimethylbenzenes, xylenes, 3-methylhexane, n-hexane and toluene are key species associated with ozone photochemical production. Formation of ozone is found to be NOx-limited as indicated by measured VOCs/NOx ratios and further confirmed by a sensitivity study using a photochemical box model NCAR_MM. The Model simulation suggests that ozone production is also sensitive to changes in VOC reactivity under the NOx-limited regime, although this sensitivity depends strongly on how much NOx is present.
Operational total and tropospheric NO2 column retrieval for GOME-2
Authors: Valks P. , Pinardi G. , Richter A. , Lambert J.-C. , Hao N. , Loyola D. , Van Roozendael M. , Emmadi S.
Published: March 2011

Abstract. This paper presents the algorithm for the operational near real time retrieval of total and tropospheric NO2 columns from the Global Ozone Monitoring Experiment (GOME-2). The retrieval is performed with the GOME Data Processor (GDP) version 4.4 as used by the EUMETSAT Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M-SAF). The Differential Optical Absorption Spectroscopy (DOAS) method is used to determine NO2 slant columns from GOME-2 (ir)radiance data in the 425–450 nm range. Initial total NO2 columns are computed using stratospheric air mass factors, and GOME-2 derived cloud properties are used to calculate the air mass factors for scenarios in the presence of clouds. To obtain the stratospheric NO2 component, a spatial filtering approach is used, which is shown to be an improvement on the Pacific reference sector method. Tropospheric air mass factors are computed using monthly averaged NO2 profiles from the MOZART-2 chemistry transport model. An error assessment shows that the random error in the GOME-2 NO2 slant columns is approximately 0.45 × 1015 molec cm−2. As a result of the improved quartz diffuser plate used in the GOME-2 instrument, the systematic error in the slant columns is strongly reduced compared to GOME/ERS-2. The estimated uncertainty in the GOME-2 tropospheric NO2 column for polluted conditions ranges from 40 to 80%. An end-to-end ground-based validation approach for the GOME-2 NO2 columns is illustrated based on MAX-DOAS measurements at the Observatoire de Haute Provence (OHP). The GOME-2 stratospheric NO2 columns are found to be in good overall agreement with coincident ground-based measurements at OHP. A time series of the MAX-DOAS and the GOME-2 tropospheric NO2 columns shows that pollution episodes at OHP are well captured by GOME-2. Monthly mean tropospheric columns are in very good agreement, with differences generally within 0.5 × 1015 molec cm−2.
The French contribution to the Global Climate Observing System
Authors: Juvanon du Vachat R.
Published: March 2011

Abstract. France is participating fully in the Global Climate Observing System (GCOS). It incorporates the following four components: meteorological and atmospheric, oceanic, terrestrial, spatial, which will be briefly presented, especially in relation with the monitoring of the climate. The presentation will give an overview of the general principles governing the GCOS system and particularly the concepts used to maintain efficiently this climate observing system for a long period of time ("from research networks to operational networks"). The presentation will cover all the four components of the GCOS system. The whole report has been published in the Fifth National Communication from France to the UNFCCC (United Nations Framework Convention on Climate Change). The presentation will give an overview of the different networks of these four domains devoted to the monitoring of climate and maintained by France and highlighting the strengths and weaknesses of this climate observing system.
Where microorganisms meet rocks in the Earth's Critical Zone
Authors: Akob D. M. , Küsel K.
Published: March 2011

Abstract. The Earth's Critical Zone (CZ) is the critical, outer shell of the Earth that provides an arena for the interplay of diverse physical, chemical, and biological processes that are fundamental for sustaining life. As microbes are the principle drivers of biogeochemical cycles, it is necessary to understand the biodiversity of the CZ unseen majority and their impact on life-sustaining processes. This review aims to summarize the factors controlling where microbes (prokaryotes and micro-eukaryotes) live within the CZ and what is known to date about their diversity and function. Microbes live in all regions of the CZ down to 5 km depth, but due to changing habitat complexity, e.g., variability in pore spaces, water, oxygen, and nutrients, their functional role changes with depth. The abundance of prokaryotes and micro-eukaryotes decreases from a maximum of 1010 or 107 cells g soil−1 up to eight orders of magnitude with depth. Symbiotic mycorrhizal fungi and free-living decomposers are best understood in soil habitats, where they are up to 103 cells g soil−1. However, little is known about their identity and impact on weathering in the deep subsurface. The relatively low abundance of micro-eukaryotes in the deep subsurface suggests that these organisms are either limited in space or nutrients or unable to cope with oxygen limitations. Since deep regions of the CZ are limited in the recent input of photosynthesis-derived carbon, microbes are dependent on deposited organic material or on chemolithoautotrophic metabolism that allows for the establishment of a complete food chain independent from the surface. However, the energy flux available might only allow cell growth over tens to thousands of years. The recent development of "omics" technologies has provided microbial ecologists with methods to link the composition and function of in situ microbial communities. We should expect new metabolic discoveries as we have a closer look utilizing a polyphasic approach into the microbial communities of the CZ. Thus, future work is still needed to link microbial biodiversity to the exact role of microbes in weathering and geochemical cycling in the CZ, especially in subsurface habitats.
Blastodinium spp. infect copepods in the ultra-oligotrophic marine waters of the Mediterranean Sea
Authors: Alves-de-Souza C. , Cornet C. , Nowaczyk A. , Gasparini S. , Skovgaard A. , Guillou L.
Published: March 2011

Abstract. Blastodinium are chloroplast-containing dinoflagellates which infect a wide range of copepods. They develop inside the gut of their host, where they produce successive generations of sporocytes that are eventually expelled through the anus of the copepod. Here, we report on copepod infections in the oligotrophic to ultra-oligotrophic waters of the Mediterranean Sea sampled during the BOUM cruise. Based on a DNA-stain screening of gut contents, 16% of copepods were possibly infected in samples from the Eastern Mediterranean, with up to 51% of Corycaeidae, 33% of Calanoida, but less than 2% of Oithonidae and Oncaeidae. Parasites were classified into distinct morphotypes, with some tentatively assigned to species B. mangini, B. contortum, and B. cf. spinulosum. Based upon the SSU rDNA gene sequence analyses of 15 individuals, the genus Blastodinium was found to be polyphyletic, containing at least three independent clusters. The first cluster grouped all sequences retrieved from parasites of Corycaeidae and Oncaeidae during this study, and included sequences of Blastodinium mangini (the "mangini" cluster). Sequences from cells infecting Calanoida belonged to two different clusters, one including B. contortum (the "contortum" cluster), and the other uniting all B. spinulosum-like morphotypes (the "spinulosum" cluster). Cluster-specific oligonucleotidic probes were designed and tested by FISH in order to assess the distribution of dinospores, the Blastodinium dispersal and infecting stage. Probe-positive cells were all small thecate dinoflagellates, with lengths ranging from 7 to 18 μm. Maximal abundances of Blastodinium dinospores were detected at the Deep Chlorophyll Maximum (DCM) or slightly below. This was in contrast to distributions of autotrophic pico- and nanoplankton, microplanktonic dinoflagellates, and nauplii which showed maximal concentrations above the DCM. The distinct distributions of dinospores and nauplii argues against infection during the naupliar stage. Blastodinium, described as autotrophic in the literature, may escape the severe nutrient limitation of ultra-oligotrophic ecosystems by living inside copepods.
Thermodynamic dissipation theory for the origin of life
Authors: Michaelian K.
Published: March 2011

Abstract. Understanding the thermodynamic function of life may shed light on its origin. Life, as are all irreversible processes, is contingent on entropy production. Entropy production is a measure of the rate of the tendency of Nature to explore available microstates. The most important irreversible process generating entropy in the biosphere and, thus, facilitating this exploration, is the absorption and transformation of sunlight into heat. Here we hypothesize that life began, and persists today, as a catalyst for the absorption and dissipation of sunlight on the surface of Archean seas. The resulting heat could then be efficiently harvested by other irreversible processes such as the water cycle, hurricanes, and ocean and wind currents. RNA and DNA are the most efficient of all known molecules for absorbing the intense ultraviolet light that penetrated the dense early atmosphere and are remarkably rapid in transforming this light into heat in the presence of liquid water. From this perspective, the origin and evolution of life, inseparable from water and the water cycle, can be understood as resulting from the natural thermodynamic imperative of increasing the entropy production of the Earth in its interaction with its solar environment. A mechanism is proposed for the reproduction of RNA and DNA without the need for enzymes, promoted instead through UV light dissipation and diurnal temperature cycling of the Archean sea-surface.
Coupled atmosphere-wildland fire modeling with WRF-Fire version 3.3
Authors: Mandel J. , Beezley J. D. , Kochanski A. K.
Published: March 2011

Abstract. We describe the physical model, numerical algorithms, and software structure of WRF-Fire. WRF-Fire consists of a fire-spread model, implemented by the level-set method, coupled with the Weather Research and Forecasting model. In every time step, the fire model inputs the surface wind, which drives the fire, and outputs the heat flux from the fire into the atmosphere, which in turn influences the atmosphere. The level-set method allows submesh representation of the burning region and flexible implementation of various kinds of ignition. WRF-Fire is distributed as a part of WRF and it uses the WRF parallel infrastructure for parallel computing.
Potential of high-resolution detection and retrieval of precipitation fields from X-band spaceborne synthetic aperture radar over land
Authors: Marzano F. S. , Mori S. , Chini M. , Pulvirenti L. , Pierdicca N. , Montopoli M. , Weinman J. A.
Published: March 2011

Abstract. X-band Synthetic Aperture Radars (X-SARs), able to image the Earth's surface at metric resolution, may provide a unique opportunity to measure rainfall over land with spatial resolution of about few hundred meters, due to the atmospheric moving-target degradation effects. This capability has become very appealing due to the recent launch of several X-SAR satellites, even though several remote sensing issues are still open. This work is devoted to: (i) explore the potential of X-band high-resolution detection and retrieval of rainfall fields from space using X-SAR signal backscattering amplitude and interferometric phase; (ii) evaluate the effects of spatial resolution degradation by precipitation and inhomogeneous beam filling when comparing to other satellite-based sensors. Our X-SAR analysis of precipitation effects has been carried out using both a TerraSAR-X (TSX) case study of Hurricane "Gustav" in 2008 over Mississippi (USA) and a COSMO-SkyMed (CSK) X-SAR case study of orographic rainfall over Central Italy in 2009. For the TSX case study the near-surface rain rate has been retrieved from the normalized radar cross section by means of a modified regression empirical algorithm (MREA). A relatively simple method to account for the geometric effect of X-SAR observation on estimated rainfall rate and first-order volumetric effects has been developed and applied. The TSX-retrieved rain fields have been compared to those estimated from the Next Generation Weather Radar (NEXRAD) in Mobile (AL, USA). The rainfall detection capability of X-SAR has been tested on the CSK case study using the repeat-pass coherence response and qualitatively comparing its signature with ground-based Mt. Midia C-band radar in central Italy. A numerical simulator to represent the effect of the spatial resolution and the antenna pattern of TRMM satellite Precipitation Radar (PR) and Microwave Imager (TMI), using high-resolution TSX-retrieved rain images, has been also set up in order to evaluate the rainfall beam filling phenomenon. As expected, the spatial average can modify the statistics of the high-resolution precipitation fields, strongly reducing its dynamics in a way non-linearly dependent on the rain rate local average value.
Temporal properties of rainfall events in Calabria (southern Italy)
Authors: Terranova O. G. , Iaquinta P.
Published: March 2011

Abstract. Temporal properties of 152 575 rainfall events, recorded at time steps of 5 min, having different durations and occurring between 1989 and 2008 at 155 localities of Calabria (Italy), have been analysed in this paper. Samples from 45 533 storms have been selected to classify rainfall events as "significant" with regard to their contribution to soil erosion, flooding and/or other geo-hydrological processes. The samples are representative of a wide variety of situations in terms of duration, total rainfall, intensity, etc. The use of standardized rainfall profiles (SRP) is proposed to describe the within-storm temporal pattern. The main attraction of this method lies in the fact that it is based on actual data of regional precipitation. Its weak point is that large samples of data are required to obtain regional profiles. The research necessities for improving the use of Huff curves for storm disaggregation and its the potential use are summarized in this paper on the basis of the specific literature. A new criterion – based on the comparison of the areas A1, A2, A3 and A4 that underlie the four 25% of durations of a given SRP, and the corresponding four values of the "uniform" SRP (USRP), is suggested here with the aim of improving the use of the information content of SRP. Some interesting results concerning the sample frequency and the characterization of parameters for hydrological applications are commented on. The study conducted so far has produced important, albeit preliminary, results for different contexts of Calabria concerning the use of SRP among the methods for constructing design storm hyetographs.
Upper ocean stratification and sea ice growth rates during the summer-fall transition, as revealed by Elephant seal foraging in the Adélie Depression, East Antarctica
Authors: Williams G. D. , Hindell M. , Houssais M.-N. , Tamura T. , Field I. C.
Published: March 2011

Abstract. Southern elephant seals (Mirounga leonina), fitted with Conductivity-Temperature-Depth sensors at Macquarie Island in January 2005 and 2010, collected unique oceanographic observations of the Adélie and George V Land continental shelf (140–148° E) during the summer-fall transition (late February through April). This is a key region of dense shelf water formation from enhanced sea ice growth/brine rejection in the local coastal polynyas. In 2005, two seals occupied the continental shelf break near the grounded icebergs at the northern end of the Mertz Glacier Tongue for several weeks from the end of February. One of the seals migrated west to the Dibble Ice Tongue, apparently utilising the Antarctic Slope Front current near the continental shelf break. In 2010, immediately after that year's calving of the Mertz Glacier Tongue, two seals migrated to the same region but penetrated much further southwest across the Adélie Depression and sampled the Commonwealth Bay polynya from March through April. Here we present observations of the regional oceanography during the summer-fall transition, in particular (i) the zonal distribution of modified Circumpolar Deep Water exchange across the shelf break, (ii) the upper ocean stratification across the Adélie Depression, including alongside iceberg C-28 that calved from the Mertz Glacier and (iii) the convective overturning of the deep remnant seasonal mixed layer in Commonwealth Bay from sea ice growth. Heat and freshwater budgets to 200–300 m are used to estimate the ocean heat content (400→50 MJ m−2), flux (50–200 W m−2 loss) and sea ice growth rates (maximum of 7.5–12.5 cm day−1). Mean seal-derived sea ice growth rates were within the range of satellite-derived estimates from 1992–2007 using ERA-Interim data. We speculate that the continuous foraging by the seals within Commonwealth Bay during the summer/fall transition was due to favorable feeding conditions resulting from the convective overturning of the deep seasonal mixed layer and chlorophyll maximum that is a reported feature of this location.
Retrieval of snow albedo and grain size using reflectance measurements in Himalayan basin
Authors: Negi H. S. , Kokhanovsky A.
Published: March 2011

Abstract. In the present paper, spectral reflectance measurements of Himalayan seasonal snow were carried out and analysed to retrieve the snow albedo and effective grain size. The asymptotic radiative transfer (ART) theory was applied to retrieve the plane and spherical albedo. The retrieved plane albedo was compared with the measured spectral albedo and a good agreement was observed with ±10% differences. Retrieved integrated albedo was found within ±6% difference with ground observed broadband albedo. The retrieved snow grain sizes using different models based on the ART theory were compared for various snow types and it was observed that the grain size model using two channel method (one in visible and another in NIR region) can work well for the Himalayan seasonal snow and it was found consistent with temporal changes in grain size. This method can work very well for clean, dry snow as in the upper Himalaya, but sometimes, due to the low reflectances (<20%) using wavelength 1.24 μm, the ART theory cannot be applied, which is common in lower and middle Himalayan old snow. This study is important for monitoring the Himalayan cryosphere using air-borne or space-borne sensors.
Policy and Practice in Education Reform in Mongolia and Uzbekistan during the First Two Decades of the Post-Soviet Era
Authors: Weidman John C. , Yoder Brian
Published: March 2011

This article describes the social, economic, and political processes that have influenced educational reform in two countries of Central Asia since the fall of the Soviet Union in 1991. It compares and contrasts the various educational reform initiatives that have occurred in each country, including legal and policy frameworks, curriculum change, decentralization, privatization, finance, structure, and emphasis of educational systems, and the fit between what is taught in educational institutions and demands of the labor market. A sector-wide framework for education reform is presented to facilitate understanding of the very complex set of processes involved.
Increasing Dialysis Access Options in Lower Extremity: Retroperitoneal Approach for External Iliac Artery-Vein Arteriovenous Graft
Authors: Colvard Benjamin D. , Anaya-Ayala Javier E. , Palacios-Reyes Deborah , Cheema Zulfiqar F. , Smolock Christopher J. , Davies Mark G. , Peden Eric K.
Published: March 2011

Background

Exhaustion of upper extremity dialysis access options is becoming more prevalent due to the longer survival of this patient population. In addition, central venous occlusive disease (CVOD) increases the risk of losing access viability in the ipsilateral extremity.

Purpose

We describe a novel technique of lower extremity arteriovenous graft (AVG) placement in which the external iliac artery and vein are utilized, as illustrated in 2 selected cases.

Methods

Two dialysis patients presented with exhausted upper extremity access options and bilateral intrathoracic CVOD. In patient 1, a venogram demonstrated complete occlusion of the left common iliac vein and severe stenosis of the right common femoral vein, rendering these unsuitable for access creation. In patient 2, with a history of peripheral arterial disease, an arteriogram revealed that the common and superficial femoral arteries were inadequate for access creation bilaterally. A retroperitoneal approach was utilized for a right external iliac artery and vein arteriovenous graft tunneled under the inguinal ligament to the anterior thigh.

Results

Adequate thrill and uneventful postoperative course were observed in both cases. At 10 months, patient 1 has done well on hemodialysis without the need for further intervention. Patient 2 has only recently had the procedure and is not yet using her graft.

Conclusions

As the number of patients requiring lower extremity vascular access increases, new surgical techniques will become available to handle the clinical and anatomic challenges encountered in this population.
Total brain white matter is a major determinant of IQ in adolescents born preterm
Authors: Northam Gemma B. , Liégeois Frédérique , Chong Wui K. , S. Wyatt John , Baldeweg Torsten
Published: March 2011

Objective

In preterm infants, white matter (WM) abnormalities detected on magnetic resonance imaging (MRI) at term‐age are associated with early developmental delay. We set out to study this association in adolescents born pre‐term, by examining intellectual outcome in relation to markers of brain injury, focusing on the effects of WM reduction.

Methods

Seventy‐nine participants were recruited and assessed at a mean age of 16 years: 49 adolescents born preterm (<32 weeks' gestation) with a wide spectrum of brain injuries (including 22 with no identifiable brain injury at birth) and 30 term‐born controls. Data collected included: brain MRI scans, full‐scale intelligence quotient (IQ) scores, educational attainments, and behavioral scores. Measures of WM reduction included total volume, cross‐sectional area of the corpus callosum (CC), and ventricular dilatation. Cerebellar volumes and neuroradiological ratings were also included.

Results

WM volume and IQ were reduced in the preterm groups (both with and without brain injury). Total WM volume and CC area jointly explained 70% of IQ variance in the adolescents born preterm, irrespective of the presence or severity of brain abnormalities detected at birth or on follow‐up MRI. This relationship was not seen in controls. Importantly, correlations were also found with real‐world measures of academic achievement and behavioral difficulties.

Interpretation

Preterm birth has a long‐term effect on cognition, behavior, and future academic success primarily as a consequence of global brain WM reduction. This emphasizes the need for early therapeutic efforts to prevent WM injury and promote or optimize its development in preterm neonates. Ann Neurol 2011
Diagnosing cerebral aneurysms by computed tomographic angiography: Meta‐analysis
Authors: Menke Jan , Larsen Jörg , Kallenberg Kai
Published: March 2011

Objective

Cerebral aneurysms can cause substantial morbidity and mortality, specifically if they rupture, leading to nontraumatic subarachnoid hemorrhage (SAH). This meta‐analysis summarizes evidence about the accuracy of noninvasive computed tomographic (CT) angiography for diagnosing intracranial aneurysms in symptomatic patients.

Methods

Four databases including PubMed were searched without language restrictions from January 1995 to February 2010. Two independent reviewers selected and extracted 45 studies that compared CT angiography with digital subtraction angiography (DSA) and/or intraoperative findings in patients suspected of having cerebral aneurysms. Data from eligible studies were used to reconstruct 2 × 2 contingency tables on a per‐patient basis in at least 5 diseased and 5 nondiseased patients, with additional data on a per‐aneurysm basis when available.

Results

The 45 included studies generally were of high methodological quality. Among the 3,643 patients included, about 86% had nontraumatic SAH, and 77% had cerebral aneurysms. Overall, CT angiography had a pooled sensitivity of 97.2% (95% confidence interval, 95.8–98.2%) for detecting and specificity of 97.9% (95.7–99.0%) for ruling out cerebral aneurysms on a per‐patient basis. On a per‐aneurysm basis, the pooled sensitivity was 95.0% (93.2–96.4%), and the specificity 96.2% (92.9–98.0%). The diagnostic accuracy of CT angiography with 16‐ or 64‐row multidetector CT was significantly higher than that of single‐detector CT, especially in detecting small aneurysms of ≤4mm in diameter.

Interpretation

CT angiography has a high accuracy in diagnosing cerebral aneurysms, specifically when using modern multidetector CT. In the future, CT angiography may increasingly supplement or selectively replace DSA in patients suspected of having a cerebral aneurysm. ANN NEUROL 2011
The complex world of oligodendroglial differentiation inhibitors
Authors: Kremer David , Aktas Orhan , Hartung Hans‐Peter , Küry Patrick
Published: March 2011

Myelination is a central nervous system (CNS) process wherein oligodendrocyte‐axon interactions lead to the establishment of myelin sheaths that stabilize, protect, and electrically insulate axons. In inflammatory demyelinating diseases such as multiple sclerosis (MS), the degeneration and eventual loss of functional myelin sheaths slows and blocks saltatory conduction in axons, which results in clinical impairment. However, remyelination can occur, and lesions can be partially repaired, resulting in clinical remission. The recruitment and activation of resident oligodendrocyte precursor cells (OPCs) play a critical role in the repair process because these cells have the capacity to differentiate into functional myelinating cells. Mature oligodendrocytes, however, are thought to have lost the capacity to develop new myelin sheaths and frequently undergo programmed cell death in MS. The endogenous capacity to generate new oligodendrocytes in MS is limited, and this is predominantly due to the presence of inhibitory components that block OPC differentiation and maturation. Here, we present an overview of recently identified negative regulators of oligodendroglial differentiation and their potential relevance for CNS repair in MS. Because currently available immunomodulatory drugs for MS mainly target inflammatory cascades outside the brain and fail to repair existing lesions, achieving more efficient lesion repair constitutes an important goal for future MS therapies. Ann Neurol 2011;69:602–618
A new graphical approach for simultaneous targeting and design of a paper recycling network
Authors: Kit Soh Guan , Wan Alwi Sharifah Rafidah , Manan Zainuddin Abdul
Published: March 2011

Rising demand for paper has resulted in increased number of trees being chopped around the world. The loss of forest lands due to rampant tree cutting has caused a steady increase in the earth's temperature, changed the weather pattern and ultimately threatened the world's ecosystems. One way to mitigate these problems is through efficient paper recycling. To ensure that maximum recycling is achieved, proper mixing of different types of paper of different fiber contents should be considered. This work presents a new generic graphical method for simultaneous targeting and designing of a maximum paper recycling network. The first step is to establish the maximum paper recycling target using a graphical approach called the source–sink composite curves. Next, source–sink allocation curve and network allocation diagram are constructed to design the maximum paper recovery network. The graphical tool allows a designer to graphically visualize, explore, evolve and systematically select the best paper recycling network. Application of the method in Universiti Teknologi Malaysia campus yields a new fresh fiber target of 1464 tons/year. This is a potential reduction in 43.7% fresh fiber and translates into an annual reduction in 38 622 chopped trees and a potential savings of up to 4.5 GWh of electricity and 30.1 × 103 m3 of water. Copyright © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.
Solid‐phase extraction and pre‐concentration of trace metals in natural waters using indigenously synthesized chelating resin and their subsequent determination by ICP‐OES
Authors: Waqar Farhat , Jan Saida , Hakim Muhammad , Mohammad Bashir , Ghaffar Abdul , Yawar Wasim
Published: March 2011

A laboratory made chelating resin based on immobilization of fluorinated β‐diketone group on styrene divinyl benzene was employed for the extraction and pre‐concentration of trace metals in natural water samples before their determination by inductively coupled plasma optical emission spectrometry (ICP‐OES). Extraction efficiency of the resin toward metal ions was examined by column procedure. Various experimental parameters consisting pH, sample loading flow rate, eluent concentration/volume and breakthrough limits were investigated for the effective uptake of metals on the resin. The resin capacity at pH (9) was found to be 10.20, 9.13, 7.47, 8.67, 3.12, 6.45 and 9.80 mg g−1 for Cd (Cadmium), Co (Cobalt), Fe (Iron), Mn (Manganese), Mo (Molybdenum), Ni (Nickel) and Zn (Zinc), respectively. The method was applied for the extraction/pre‐concentration of Cd, Co, Fe, Mn, Mo, Ni and Zn in natural water samples and their subsequent determination was carried out by ICP‐OES. Percentage recoveries obtained for the selected metals except Mo were ≥ 95% under similar experimental conditions with < 5% relative standard deviation. Alkali/alkaline earth metals, the major matrix ions were not retained on the resin, the resin is selective for trace metals, therefore it is suitable for the extraction of these metals in natural water samples for environmental and health‐related studies. © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.
Exploration of dual optimal conditions for COD and nitrogen removal in an MBR
Authors: Lim JungJin , Lee YouLim , Ataei Abtin , Yoo ChangKyoo
Published: March 2011

Membrane bioreactors (MBRs) have been increasingly used for wastewater treatment in last decade. MBR process has several characteristics such as high sludge retention time, high mixed liquor concentration and accumulation of soluble microbial products. Although activated sludge models (ASMs) have been developed for conventional activated sludge process, applying the ASM model to MBR process seems to be proper. In this study, a model‐based systematic approach that can find optimal operational conditions for chemical oxygen demand (COD) and nitrogen removal was explored to a MBR process. To enhance the modeling performance of the ASM, the precise influent characterization for MBR process was performed by using a respirometry. The optimization results in MBR plant showed that the removal efficiencies of COD and nitrogen in the plant were greatly improved to 88.10 and 62.67%, respectively. Copyright © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.
Life expectancy, standardized mortality ratios, and causes of death in six rheumatic diseases in Hong Kong, China
Authors: Mok C. C. , Kwok C. L. , Ho L. Y. , Chan P. T. , Yip S. F.
Published: March 2011

Objective

To examine the life expectancy, standardized mortality ratios (SMRs), and causes of death in 6 groups of patients from Hong Kong with different rheumatic diseases.

Methods

Patients with a diagnosis of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), ankylosing spondylitis (AS), psoriatic arthritis (PsA), systemic vasculitis (SV), or systemic sclerosis (SSc) registered in 37 public hospitals between 1999 and 2008 were identified in the hospital registry. SMRs were calculated by comparing the mortality rate in patients with each disease with that in the general population. Life expectancy was calculated by abridged life‐table analysis, and the causes of death were compared.

Results

In 2008, data on 8,367 RA, 5,243 SLE, 2,154 AS, 1,636 SV, 778 PsA, and 449 SSc patients were available in our registry. The age‐ and sex‐adjusted SMRs were highest for SLE (5.25 [95% confidence interval 4.79–5.70]), SSc (3.94 [95% confidence interval 3.20–4.68]), and SV (2.64 [95% confidence interval 2.36–2.93]). In female patients, the loss in life expectancy was greatest for SSc (34.1 years), SV (19.3 years), and SLE (19.7 years). In male patients, the loss in life expectancy was highest for SV (28.3 years), SLE (27 years), and SSc (16 years). There were 2,486 deaths during the study period (1999–2008), and the principal causes were infections (28%), cardiovascular complications (18%), cancer (16%), and disease activity (7%). Infection was the leading cause of death in SLE, RA, AS, and PsA, whereas deaths from disease‐related activity and cardiovascular complications were most frequent in SSc. Cancer was the most common cause of death in SV.

Conclusion

Our findings indicate that patients with SLE, RA, AS, PsA, SV, and SSc have increased mortality rates and reduced life expectancy. SLE has the highest adjusted SMR, and female SSc patients have the greatest loss in life expectancy. Infection is the leading cause of death, followed by cardiovascular complications and malignancies.
A novel concept combining experimental and mathematical analysis for the identification of unknown interspecies effects in a mixed culture
Authors: Schmidt Julia K. , Riedele Christian , Regestein Lars , Rausenberger Julia , Reichl Udo
Published: March 2011

Bacteria in natural habitats only occur in consortia together with various other species. Characterization of bacterial species, however, is normally done by laboratory testing of pure isolates. Any interactions that might appear during growth in mixed‐culture are obviously missed by this approach. Existing experimental studies mainly focus on two‐species mixed cultures with species specifically chosen for their known growth characteristics, and their anticipated interactions. Various theoretical mathematical studies dealing with mixed cultures and possible interspecies effects exist, but often models cannot be validated due to a lack of experimental data. Here, we present a concept for the identification of interspecies effects in mixed cultures with arbitrary and unknown single‐species properties. Model structure and parameters were inferred from single‐species experiments for the reproduction of mixed‐culture experiments by simulation. A mixed culture consisting of the three‐species Pseudomonas aeruginosa, Burkholderia cepacia, and Staphylococcus aureus served as a model system. For species‐specific enumeration a quantitative terminal restriction length polymorphism (qT‐RFLP) assay was used. Based on models fitted to single‐species cultivations, the outcome of mixed‐culture experiments was predicted. Deviations of simulation results and experimental findings were then used to design additional single‐cell experiments, to modify the corresponding growth kinetics, and to update model parameters. Eventually, the resulting mixed‐culture dynamics was predicted and compared again to experimental results. During this iterative cycle, it became evident that the observed coexistence of P. aeruginosa and B. cepacia in mixed‐culture chemostat experiments cannot be explained on the basis of glucose as the only substrate. After extension of growth kinetics, that is, for use of amino acids as secondary substrates, mixed‐culture simulations represented the experimental findings very well. According to the model structure, as motivated by single‐species experiments, the growth of P. aeruginosa and B. cepacia on glucose and amino acids could be assumed to be independent of each other. In contrast, both substrates are taken up simultaneously by S. aureus. Biotechnol. Bioeng. 2011; 108:1900–1911. © 2011 Wiley Periodicals, Inc.