bluuebunny/crossref_metadata_2025 huggingface dataset:
Mapping and monitoring land degradation risks in the Western Brazilian Amazon using multitemporal Landsat TM/ETM+ images
Authors: Lu D. , Batistella M. , Mausel P. , Moran E.
Published: August 2006

Mapping and monitoring land degradation in areas under human‐induced stresses have become urgent tasks in remote sensing whose importance has not yet been fully appreciated. In this study, a surface cover index (SCI) is developed to evaluate and map potential land degradation risks associated with deforestation and accompanying soil erosion in a Western Brazilian Amazon rural settlement study area. The relationships between land‐use and land‐cover (LULC) types and land degradation risks as well as the impacts of LULC change on land degradation are examined. This research indicates that remotely sensed data can be effectively used for identification and mapping of land degradation risks and monitoring of land degradation changes in the study area. Sites covered by mature forest and advanced successional forests have low land degradation risk potential, while some types of initial successional forests, agroforestry/perennial agriculture and pasture have higher risk potential. Deforestation and associated soil erosion are major causes leading to land degradation, while vegetation regrowth reduces such problems. Copyright © 2006 John Wiley & Sons, Ltd.
Anti‐apoptotic effect of insulin‐like growth factor (IGF)‐I and its receptor in porcine preimplantation embryos derived from in vitro fertilization and somatic cell nuclear transfer
Authors: Kim Sue , Lee So Hyun , Kim Ji Hye , Jeong Yeon Woo , Hashem M.A. , Koo Ok Jae , Park Sun Mi , Lee Eu Gine , Hossein M.S. , Kang Sung Keun , Lee Byeong Chun , Hwang Woo Suk
Published: August 2006

Insulin‐like growth factor (IGF)‐I is a receptor‐mediated autocrine and/or paracrine growth and/or survival factor for mammalian embryo development. It is known to promote the growth and development of mouse preimplantation embryos. The present study was designed to investigate the effects of IGF‐I (50 ng/ml), anti‐IGF‐I receptor antibody (50 ng/ml) and their combination on porcine preimplantation embryo development. Furthermore, the mechanism underlying the embryotropic effects of IGF‐I was evaluated by monitoring the incidence of apoptosis and expression of apoptosis‐related genes. In both in vitro fertilized (IVF) and somatic cell nuclear transfer (SCNT) embryos, culturing with IGF‐I increased the rate of blastocyst formation and this embryotrophic effect was neutralized by culturing with IGF‐I along with anti‐IGF‐I receptor (IGF‐IR) antibody. Culturing IVF and SCNT embryos with IGF‐I significantly increased the number of total cells in blastocysts and decreased the number of apoptotic nuclei. These effects of IGF‐I were also neutralized by culturing with IGF‐I along with anti‐IGF‐IR antibody. Expression of the anti‐apoptotic Bcl‐2 gene was increased, while expression of the pro‐apoptotic Bax was decreased in both IVF and SCNT embryos cultured with IGF‐I. In both IVF and SCNT embryos, anti‐IGF‐IR antibody along with IGF‐I neutralized the effect of IGF‐I on expression of Bcl‐2 and Bax genes. In conclusion, the present study demonstrated that IGF‐I through its specific receptors improved the developmental competence of IVF and SCNT embryos by decreasing the incidence of apoptosis and regulating apoptosis‐related genes in porcine preimplantation embryos. Mol. Reprod. Dev. 73: 1523–1530, 2006. © 2006 Wiley‐Liss, Inc.
Mass spectrometry as a tool in dendrimer chemistry: from self‐assembling dendrimers to dendrimer gas‐phase host–guest chemistry
Authors: Schalley Christoph A. , Baytekin Bilge , Baytekin H. Tarik , Engeser Marianne , Felder Thorsten , Rang Alexander
Published: August 2006

Mass spectrometry has played a significant role in dendrimer chemistry, because it serves as an excellent analytical means to determine the purity and analyze the nature of defects even for higher generations. However, a mass spectrometer can also be used as a laboratory to study isolated dendrimer molecules in the gas phase or their host–guest complexes. Since the properties of molecules under environment‐free conditions are often quite different from those in solution, their gas‐phase chemistry provides valuable new insight into properties which cannot easily be studied in solution. This article summarizes some of our work on characterizing self‐assembling metallo‐supramolecular dendrimers, on analyzing ionization artifacts, on the differentiation between several, sometimes even isomeric defects through tandem MS experiments, and finally on the analysis of a surprisingly clear dendritic effect occurring in the fragmentation of dendritic host–guest complexes. Copyright © 2006 John Wiley & Sons, Ltd.
Coarse graining in block copolymer films
Authors: Tsori Yoav , Andelman David
Published: August 2006

We present few ordering mechanisms in block copolymer melts in the coarse‐graining approach. For chemically homogeneous or modulated confining surfaces, the surface ordering is investigated above and below the order–disorder temperature. In some cases, the copolymer deformation near the surface is similar to the copolymer morphology in bulk grain boundaries. Block copolymers in contact with rough surfaces are considered as well, and the transition from lamellae parallel to perpendicular to the surface is investigated as a function of surface roughness. Finally, we describe how external electric fields can be used to align block copolymer mesophases in a desired direction, or to induce an order–order phase transition, and dwell on the role of mobile dissociated ions on the transition. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2725–2739, 2006
Can low‐power electromagnetic radiation disrupt hydrogen bonds in dsDNA?
Authors: Chitanvis Shirish M.
Published: August 2006

Microwave radiation resonant with the natural phonon frequencies of double‐stranded DNA (dsDNA) is shown to couple strongly to the breather modes of dsDNA under certain conditions. The excitation of the disruptive breather modes is controlled to a great extent by energy dissipation to its aqueous environment. For sufficiently high power—much higher than expected under ambient conditions—the breather solutions become unstable. Our analysis discounts the disruptive effect of low frequency, low power radiation on dsDNA. The authors hope to stimulate experiments via their analysis. The resulting data will dictate the future evolution of their models. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2740–2747, 2006
Comparing the impact of conventional pesticide and use of a transgenic pest‐resistant crop on the beneficial carabid beetle Pterostichus melanarius
Authors: Mulligan Evan A , Ferry Natalie , Jouanin Lise , Walters Keith FA , Port Gordon R , Gatehouse Angharad MR
Published: August 2006

The potential impact of a chemical pesticide control method has been compared with that of transgenic plants expressing a protease inhibitor conferring insect resistance by utilising a tritrophic system comprising the crop plant Brassica napus (L.) (Oilseed rape), the pest mollusc Deroceras reticulatum (Müller) and the predatory carabid beetle Pterostichus melanarius (Illiger). Cypermethrin, as the most widely used pesticide in UK oilseed rape (OSR) cultivation, was selected as the conventional treatment. OSR expressing a cysteine protease inhibitor, oryzacystatin‐1 (OC‐1), was the transgenic comparator. In feeding trials, D. reticulatum showed no significant long‐term effects on measured life history parameters (survival, weight gain, food consumption) as a result of exposure to either the cypermethrin or OC‐1 treatment. However, D. reticulatum was able to respond to the presence of the dietary inhibitor by producing two novel proteases following exposure to OC‐1‐expressing OSR. Similarly, P. melanarius showed no detectable alterations in mortality, weight gain or food consumption when feeding on D. reticulatum previously fed either pesticide‐contaminated or GM plant material. Furthermore, as with the slug, a novel form of protease, approximately Mr 27 kDa, was induced in the carabid in response to feeding on slugs fed OC‐1‐expressing OSR. Copyright © 2006 Society of Chemical Industry
Multivariate time‐to‐event analysis of multiple adverse events of drugs in integrated analyses
Authors: Güttner Achim , Kübler Jürgen , Pigeot Iris
Published: August 2006

In each clinical trial the statistical evaluation of adverse events (AEs) is a major part of standard safety analyses. However, the analyses of AEs usually lack from adequately accounting for the occurrence of multiple, different AEs. Furthermore, predictive variables other than treatment such as age, sex and concomitant medication are often ignored. These issues can be addressed by the Cox regression as introduced by Andersen and Gill and Wei et al. A further issue arises from the fact that an ordered programme of studies is conducted during clinical testing of pharmaceutical drugs. In this paper, we therefore discuss a stratified multivariate Cox regression model that can be used in integrated summaries of safety. We derive partial maximum likelihood estimators of the model parameters which can be shown to be consistent and asymptotically normally distributed. Mainly based on a sandwich estimator of their covariance matrix several test statistics are proposed that can be used to test various null hypotheses on the underlying parameters. Their asymptotic null distributions are given. The benefit of this survival time approach for analysing AEs is illustrated by evaluating symptoms of common cold from the database of a clinical development project. Copyright © 2006 John Wiley & Sons, Ltd.
Trying to be precise about vagueness
Authors: Senn Stephen
Published: August 2006

A previous investigation by Lambertet al., which used computer simulation to examine the influence of choice of prior distribution on inferences from Bayesian random effects meta‐analysis, is critically examined from a number of viewpoints. The practical example used is shown to be problematic. The various prior distributions are shown to be unreasonable in terms of what they imply about the joint distribution of the overall treatment effect and the random effects variance. An alternative form of prior distribution is tentatively proposed. Finally, some practical recommendations are made that stress the value both of fixed effect analyses and of frequentist approaches as well as various diagnostic investigations. Copyright © 2006 John Wiley & Sons, Ltd.
Flexible random‐effects models using Bayesian semi‐parametric models: applications to institutional comparisons
Authors: Ohlssen D. I. , Sharples L. D. , Spiegelhalter D. J.
Published: August 2006

Random effects models are used in many applications in medical statistics, including meta‐analysis, cluster randomized trials and comparisons of health care providers. This paper provides a tutorial on the practical implementation of a flexible random effects model based on methodology developed in Bayesian non‐parametrics literature, and implemented in freely available software. The approach is applied to the problem of hospital comparisons using routine performance data, and among other benefits provides a diagnostic to detect clusters of providers with unusual results, thus avoiding problems caused by masking in traditional parametric approaches. By providing code for Winbugs we hope that the model can be used by applied statisticians working in a wide variety of applications. Copyright © 2006 John Wiley & Sons, Ltd.
Verifying data refinements using a model checker
Authors: Smith Graeme , Derrick John
Published: August 2006

In this paper, we consider how refinements between state-based specifications (e.g., written in Z) can be checked by use of a model checker. Specifically, we are interested in the verification of downward and upward simulations which are the standard approach to verifying refinements in state-based notations. We show how downward and upward simulations can be checked using existing temporal logic model checkers.

In particular, we show how the branching time temporal logic CTL can be used to encode the standard simulation conditions. We do this for both a blocking, or guarded, interpretation of operations (often used when specifying reactive systems) as well as the more common non-blocking interpretation of operations used in many state-based specification languages (for modelling sequential systems). The approach is general enough to use with any state-based specification language, and we illustrate how refinements between Z specifications can be checked using the SAL CTL model checker using a small example.
Endovascular repair of innominate artery true aneurysm with extra-anatomic revascularization of right carotid and vertebral arteries — A case report
Authors: Chang John B. , Stein Theodore , Siegel David , Rosca Mihai
Published: August 2006

The purpose of this article is to describe the endovascular repair of a large aneurysm of the innominate artery in a patient with a history of chronic renal failure and coronary artery bypass. A 4.5 × 4.8-cm innominate artery aneurysm that extended to the proximal subclavian artery was diagnosed by chest X-ray, computed tomography, computed tomography angiography, and aortic arch angiogram in an 80-year-old man who had problems with his angio access for renal dialysis. Since these aneurysms are potential sources of emboli to the brain, extra-anatomic diversion and revascularization of the right carotid and vertebral arteries were done before endovascular manipulation of the innominate artery. Before discharge, a computed tomography scan showed no evidence of a Type I or major Type II leak. The patient has been doing well as an outpatient. Large innominate artery aneurysms in high-risk patients can be treated successfully by using a combined approach of extra-anatomic revascularization of the right carotid and vertebral artery system, and endovascular repair of the aneurysm.
Healthy mind in healthy body? A review of sensorimotor–cognitive interdependencies in old age
Authors: Schäfer Sabine , Huxhold Oliver , Lindenberger Ulman
Published: August 2006

We review four broad lines of research on couplings between sensorimotor and cognitive aging, with an emphasis on methodological concerns. First, correlational cross-sectional and longitudinal data indicate increasing associations between sensorimotor and cognitive aspects of behavior with advancing age. Second, older adults show greater performance decrements than young adults when sensorimotor and cognitive tasks or task components need to be performed concurrently rather than in isolation. Third, aerobic fitness interventions produce positive transfer effects on cognition that are particularly pronounced for tasks with high demands on attention and executive control. Fourth, neuroscience findings from animal models and humans have identified aging-sensitive structural and functional circuitries that support cognitive functions and are enhanced by higher levels of sensorimotor functioning. We conclude that sensorimotor and cognitive aging are causally related and functionally interdependent and that age-associated increments in cognitive resource demands of sensorimotor functioning are malleable by experience.
Phosphorylation of C6‐ and C3‐positions of glucosyl residues in starch is catalysed by distinct dikinases
Authors: Ritte Gerhard , Heydenreich Matthias , Mahlow Sebastian , Haebel Sophie , Kötting Oliver , Steup Martin
Published: August 2006

Glucan, water dikinase (GWD) and phosphoglucan, water dikinase (PWD) are required for normal starch metabolism. We analysed starch phosphorylation in Arabidopsis wild‐type plants and mutants lacking either GWD or PWD using 31P NMR. Phosphorylation at both C6‐ and C3‐positions of glucose moieties in starch was drastically decreased in GWD‐deficient mutants. In starch from PWD‐deficient plants C3‐bound phosphate was reduced to levels close to the detection limit. The latter result contrasts with previous reports according to which GWD phosphorylates both C6‐ and C3‐positions. In these studies, phosphorylation had been analysed by HPLC of acid‐hydrolysed glucans. We now show that maltose‐6‐phosphate, a product of incomplete starch hydrolysis, co‐eluted with glucose‐3‐phosphate under the chromatographic conditions applied. Re‐examination of the specificity of the dikinases using an improved method demonstrates that C6‐ and C3‐phosphorylation is selectively catalysed by GWD and PWD, respectively.
The membrane bound bacterial lipocalin Blc is a functional dimer with binding preference for lysophospholipids
Authors: Campanacci Valérie , Bishop Russell E. , Blangy Stéphanie , Tegoni Mariella , Cambillau Christian
Published: August 2006

Lipocalins, a widespread multifunctional family of small proteins (15–25 kDa) have been first described in eukaryotes and more recently in Gram‐negative bacteria. Bacterial lipocalins belonging to class I are outer membrane lipoproteins, among which Blc from E. coli is the better studied. Blc is expressed under conditions of starvation and high osmolarity, conditions known to exert stress on the cell envelope. The structure of Blc that we have previously solved (V. Campanacci, D. Nurizzo, S. Spinelli, C. Valencia, M. Tegoni, C. Cambillau, FEBS Lett. 562 (2004) 183–188.) suggested its possible role in binding fatty acids or phospholipids. Both physiological and structural data on Blc, therefore, point to a role in storage or transport of lipids necessary for membrane maintenance. In order to further document this hypothesis for Blc function, we have performed binding studies using fluorescence quenching experiments. Our results indicate that dimeric Blc binds fatty acids and phospholipids in a micromolar K
d range. The crystal structure of Blc with vaccenic acid, an unsaturated C18 fatty acid, reveals that the binding site spans across the Blc dimer, opposite to its membrane anchored face. An exposed unfilled pocket seemingly suited to bind a polar group attached to the fatty acid prompted us to investigate lyso‐phospholipids, which were found to bind in a nanomolar K
d range. We discuss these findings in terms of a potential role for Blc in the metabolism of lysophospholipids generated in the bacterial outer membrane.
Molecular cloning and expression of icarapin, a novel IgE‐binding bee venom protein
Authors: Peiren Nico , de Graaf Dirk C. , Brunain Marleen , Bridts Chris H. , Ebo Didier G. , Stevens Wim J. , Jacobs Frans J.
Published: August 2006

The 1045 bp full‐length cDNA sequence of a new bee venom component was obtained by rapid amplification of cDNA ends. The 672 bp coding sequence corresponds to a protein with a signal peptide and multiple carbohydrate binding sites, and it was named icarapin. It has the new consensus sequence N‐[TS]‐T‐S‐[TV]‐x‐K‐[VI](2)‐[DN]‐G‐H‐x‐V‐x‐I‐N‐[ED]‐T‐x‐Y‐x‐[DHK]‐x(2,6)‐ [STA]‐[VLFI]‐x‐[KR]‐V‐R‐[VLI]‐[IV]‐[DN]‐V‐x‐P. At least two transcript variants were found. Recombinant icarapin was tested for recognition by IgE antibodies and gave a positive dot blot with sera from 4 out of 5 bee venom allergic patients, all beekeepers. Indirect immunofluorescent staining localized the protein in the cuticular lining of the venom duct.
Efficacy of steroid injection on idiopathic sudden sensorineural hearing loss
Authors: Roebuck Jeremy , Chang C. Y. Joseph
Published: August 2006

Objective

To evaluate the effectiveness of transtympanic steroid injection on patients with idiopathic sudden sensorineural hearing loss compared with patients who receive oral steroids alone.

Study Design

Retrospective chart review.

Methods

Patients with a history of ISSNHL and failed oral steroid therapy were included. Audiograms were performed and patients were included if SNHL of more than 20 dB occurred over less than 72 hours. Patients who received transtympanic steroid injection were compared with those who received oral steroids alone.

Results

Sixty‐one patients met inclusion criteria and were included in the study. The number of patients with improvement in pure tone average in the injection group was 9 (30%) compared with 5 (17%) in the oral group. Twelve (38.7%) of the injected patients did have improvement in speech discrimination scores of greater than 15% compared with only 3 (10%) in the oral steroid group.

Conclusion

Our study revealed that patients with ISSNHL who have failed oral steroid therapy obtain better hearing results with transtympanic steroids in comparison to oral steroids.

EBM rating: B‐3b
Holocene Paleoclimates of Southern Arabia from Lacustrine Deposits of the Dhamar Highlands, Yemen
Authors: Davies Caroline Pickens
Published: August 2006

This paper presents new evidence from the Dhamar highlands, Yemen, of paleohydrologic response to fluctuations in Holocene climate. Stratigraphic, geochemical, and chronological analyses of highland peat and lacustrine deposits contribute to knowledge of the timing of early Holocene moisture changes on the Arabian Peninsula, providing a backdrop to understanding early cultural development in the Arabian highlands. The location of the Dhamar highlands, characterized by intermontane valleys surrounded by the highest mountains on the Arabian Peninsula and adjacent to the Indian Ocean is ideal for examining the influence of the Indian Ocean Monsoon (IOM) on the moisture history of this region. Fluctuations in the lacustrine and paleosol records of the Dhamar highlands reflect both local changes in paleohydrology and regional influences on the Holocene paleoclimatic conditions in southwest Arabia. In addition, a peat deposit with a radiocarbon age of 10,253 ± 10,560 cal yr BP documents some of the earliest Holocene high moisture conditions on the Arabian Peninsula.
Coastal salt marshes as global methyl halide sources from determinations of intrinsic production by marsh plants
Authors: Manley Steven L. , Wang Nun‐Yii , Walser Maggie L. , Cicerone Ralph J.
Published: August 2006

Emissions of CH3Cl, CH3Br and CH3I were measured biweekly for 12‐ to 24‐month periods between March 2002 and March 2005 from monospecific stands of four dominant southern California coastal salt marsh plants. These measurements revealed large inherent differences between species and more detailed patterns of seasonal production than previously reported. Marsh plants displayed intrinsic abilities to produce methyl halides. Salt marsh plants produced 92% of CH3Cl and 90% of CH3Br emitted and only 41% of the emitted CH3I. Unvegetated areas emitted 7.9% of CH3Cl, 9.9% CH3Br, and 59% of the emitted CH3I. The accuracy of the estimated methyl halide emissions from a coastal marsh and probably other ecosystems can be dramatically improved with increasing the number of species being measured and including emission from barren (mudflats and soil) areas. Estimates of global salt marsh emissions based on vegetated and barren area are 130, 21, 5.5 (mg m−2 yr−1) for CH3Cl, CH3Br, and CH3I, respectively, or 1.2, 3.9, and 0.8% of total global fluxes of these gases.
Patterns of stress and strain rate in southern Africa
Authors: Bird Peter , Ben‐Avraham Zvi , Schubert Gerald , Andreoli Marco , Viola Giulio
Published: August 2006

The southward propagation of the East Africa rift presents an opportunity to study plate boundary formation. We tabulate orientation data which confirm the province of NW‐SE directed most compressive horizontal principal stress (“Wegener stress anomaly”) earlier tentatively attributed to ridge push. We also collect information on stress “regime,” described by the associated Andersonian fault type(s). We use thin shell finite element models with realistic rheology to test three causes of stress: (1) lateral variations in density moment, (2) resistance of unbroken lithosphere to relative plate rotation, and (3) stress concentration ahead of a crack tip. Models with stress due primarily to variations in density moment are unsuccessful in their predictions (59–73% incorrect regimes; 32–40° azimuth errors). Models in which Africa‐Somalia spreading is regulated at realistic rates by remote boundary conditions are more accurate (18–41% incorrect regimes; 25–35° azimuth errors). Treating the East Africa rift as a frictionless crack degrades the fit in either case. Apparently, the Wegener stress anomaly is caused primarily by resistance to the relative rotation between the Somalia and Africa plates. The East Africa rift north of 21°S may be weakened by strain but has residual friction ≥0.1. Greater strength of oceanic lithosphere is likely to cause stress increases, reorientations, and regime changes offshore. The predicted strain rate map has high rates along the rift, curving at 12°S into a western arc through Angola‐Namibia‐South Africa. Seismic hazard in Namibia may be greater than the instrumental catalog suggests. However, a number of unfit data indicate that these models represent only a first step.
Millennial slip rate of the Longitudinal Valley fault from river terraces: Implications for convergence across the active suture of eastern Taiwan
Authors: Shyu J. Bruce H. , Sieh Kerry , Avouac Jean‐Philippe , Chen Wen‐Shan , Chen Yue‐Gau
Published: August 2006

The Longitudinal Valley fault is a key element in the active tectonics of Taiwan. It is the principal structure accommodating convergence across one of the two active sutures of the Taiwan orogeny. To understand more precisely its role in the suturing process, we analyzed fluvial terraces along the Hsiukuluan River, which cuts across the Coastal Range in eastern Taiwan in the fault's hanging wall block. This allowed us to determine both its subsurface geometry and its long‐term slip rate. The uplift pattern of the terraces is consistent with a fault‐bend fold model. Our analysis yields a listric geometry, with dips decreasing downdip from about 50° to about 30° in the shallowest 2.5 km. The Holocene rate of dip slip of the fault is about 22.7 mm/yr. This rate is less than the 40 mm/yr rate of shortening across the Longitudinal Valley derived from GPS measurements. The discrepancy may reflect an actual difference in millennial and decadal rates of convergence. An alternative explanation is that the discrepancy is accommodated by a combination of slip on the Central Range fault and subsidence of the Longitudinal Valley floor. The shallow, listric geometry of the Longitudinal Valley fault at the Hsiukuluan River valley differs markedly from the deep listric geometry illuminated by earthquake hypocenters near Chihshang, 45 km to the south. We hypothesize that this fundamental along‐strike difference in geometry of the fault is a manifestation of the northward maturation of the suturing of the Luzon volcanic arc to the Central Range continental sliver.
The Mw 7.8, 2001 Kunlunshan earthquake: Extreme rupture speed variability and effect of fault geometry
Authors: Robinson D. P. , Brough C. , Das S.
Published: August 2006

By analyzing body wave seismograms, we show that the rupture speed on the Main Kunlun Fault during the Mw 7.8 2001 Kunlunshan, Tibet, earthquake was highly variable and the rupture process consisted of three stages. In the first stage, the rupture accelerated from rest to an average speed of 3.3 km/s over a distance of 120 km. The rupture then propagated for another 150 km at an apparent rupture speed exceeding the P wave speed. In the final stage, the earthquake fault bifurcates, and the rupture front slowed down. The region of highest rupture velocity is found to coincide with the region of highest fault slip, has the longest slip duration, and is where off‐fault ground cracking is observed in the field. Stress drops are found to be higher in regions of higher rupture speeds. The greatest concentration of aftershocks is located near the fault bifurcation zone and hence coincides with the region of highest fault slip, highest stress drop and highest rupture velocity. The fault width is no more than 10 km in most places and is about 20 km in the region of highest slip. This narrow fault width is attributed to the fact that crust below this depth is sufficiently warm not to permit brittle failure to occur. The remarkable similarity of this earthquake with the 1906 California earthquake, in spite of occurring in very different tectonic regimes, is discussed.
Nitrogen isotope constraints on subantarctic biogeochemistry
Authors: DiFiore Peter J. , Sigman Daniel M. , Trull Thomas W. , Lourey Martin J. , Karsh Kristen , Cane Greg , Ho Ruby
Published: August 2006

We report nitrate (NO3−) nitrogen isotope ratios for seawater samples collected in the Subantarctic Zone of the Southern Ocean during both winter and summer as part of the Australian Antarctic CRC Subantarctic Zone (SAZ) Project. The concentration and 15N/14N of the wintertime surface nitrate are very close to those of the subantarctic thermocline. The 15N/14N of nitrate in the surface increases sharply into the summer even though there is little seasonal change in nitrate concentration. There are two possible end‐member explanations for this observation. First, there may be significant equatorward nitrate transport during the summer, including a supply from the Antarctic surface. Second, the isotope effect of algal nitrate assimilation may be higher than has been estimated elsewhere, for example, for the seasonal sea ice zone of the Antarctic. We use a simple geochemical box model of the SAZ surface mixed layer as it evolves over the course of the summer to simulate salinity, nitrate concentration, and the 15N/14N of nitrate and sinking N. Our results suggest that a significant portion (∼30%) of the summertime SAZ nitrate is supplied from south of the Subantarctic Front and that N export is ≥3.5 mmol N m−2 d−1. Our approach also identifies the necessity of an isotope effect for nitrate assimilation in the SAZ of ≥7‰ and probably 8–9‰. Comparison to laboratory results suggests that this relatively high isotope effect may result from light limitation of algal growth in the SAZ.
Modeling production and climate‐related impacts on 10Be concentration in ice cores
Authors: Field Christy V. , Schmidt Gavin A. , Koch Dorothy , Salyk Colette
Published: August 2006

The connection between the production of the cosmogenic isotope 10Be and changes in heliomagnetic activity makes ice core 10Be an attractive proxy for studying changes in solar output. However, interpreting 10Be ice core records on centennial timescales is complicated by potential climate‐related deposition changes that could obscure the 10Be production signal. By using the Goddard Institute for Space Studies ModelE general circulation model to selectively vary climate and production functions, we model 10Be flux at key ice‐coring sites. We vary geomagnetic field strength and the solar activity modulation parameter (ϕ), CO2, sea surface temperatures, and volcanic aerosols to assess impacts on 10Be. Specifically, we find significant latitudinal differences in the response of 10Be fluxes to changes in the production function. In the climate experiments the 10Be deposition changes simulated over ice sheets in both hemispheres are comparable to those seen in the production experiments. This altered deposition combined with changes of snow accumulation results in significant climate‐related 10Be concentration variation in both Greenland and Antarctica. Over the Holocene our results suggest that the 10Be response to climate change should not be neglected when inferring production changes.
Interaction of ice storms and management practices on current carbon sequestration in forests with potential mitigation under future CO2 atmosphere
Authors: McCarthy Heather R. , Oren Ram , Kim Hyun‐Seok , Johnsen Kurt H. , Maier Chris , Pritchard Seth G. , Davis Micheal A.
Published: August 2006

Ice storms are disturbance events with potential impacts on carbon sequestration. Common forest management practices, such as fertilization and thinning, can change wood and stand properties and thus may change vulnerability to ice storm damage. At the same time, increasing atmospheric CO2 levels may also influence ice storm vulnerability. Here we show that a nonintensively managed pine plantation experienced a ∼250 g C m−2 reduction in living biomass during a single storm, equivalent to ∼30% of the annual net ecosystem carbon exchange of this ecosystem. Drawing on weather and damage survey data from the entire storm cell, the amount of C transferred from the living to the dead biomass pool (26.5 ± 3.3 Tg C), 85% of which will decompose within 25 years, was equivalent to ∼10% of the estimated annual sequestration in conterminous U.S. forests. Conifer trees were more than twice as likely to be killed as leafless deciduous broadleaf trees. In the Duke Forest case study, nitrogen fertilization had no effect on storm‐induced carbon transfer from the living to detrital pool while thinning increased carbon transfer threefold. Elevated CO2 (administered with the free‐air CO2 enrichment (FACE) system) reduced the storm‐induced carbon transfer to a third. Because of the lesser leaf area reduction, plots growing under elevated CO2 also exhibited a smaller reduction in biomass production the following year. These results suggest that forests may suffer less damage during each ice storm event of similar severity in a future with higher atmospheric CO2.
Heterogeneous uptake of nitric acid on Na‐montmorillonite clay as a function of relative humidity
Authors: Mashburn C. D. , Frinak E. K. , Tolbert M. A.
Published: August 2006

Atmospheric mineral aerosol is a potentially important reactive surface that may provide a heterogeneous sink for gas phase species such as nitric acid (HNO3). We have studied the uptake of HNO3 on Na‐montmorillonite, a swelling clay mineral, at low temperatures as a function of relative humidity (RH), HNO3 pressure and clay mass. Condensed phase products were probed with transmission Fourier transform infrared spectroscopy while the loss of HNO3 from the gas phase was simultaneously monitored with mass spectrometry. We find that below 16% RH, uptake of HNO3 on Na‐montmorillonite is below our detection limit. However, at 29% RH the lower limit to the uptake coefficient for loss of HNO3 on Na‐montmorillonite is γ = 8 × 10−5 as calculated using the BET surface area. This value increases to γ = 4 × 10−4 at 44% RH. The HNO3 content, water content and γ all increase with increasing RH, but are independent of temperature from 210 to 232 K and independent of pressure from 1 × 10−5 to 3 × 10−4 torr HNO3. Surprisingly, at 44% RH, Na‐montmorillonite can contain approximately 20% water and 30% HNO3 by weight. The results of this study suggest that swelling clays can impact the partitioning of gas phase HNO3 when sufficient water vapor is available and may serve as a potentially important cloud condensation nucleus in the troposphere.
A long Saharan dust event over the western Mediterranean: Lidar, Sun photometer observations, and regional dust modeling
Authors: Pérez C. , Nickovic S. , Baldasano J. M. , Sicard M. , Rocadenbosch F. , Cachorro V. E.
Published: August 2006

A long Saharan dust event affected the western Mediterranean in the period 12–28 June 2002. Dust was present mainly between 1‐ and 5‐km height affecting most parts of the Iberian Peninsula and reaching western/central Europe. Intensive backscatter lidar observations over Barcelona (Spain) and Sun photometer data from two stations (El Arenosillo, Spain, and Avignon, France) are used to evaluate different configurations the Dust Regional Atmospheric Modeling (DREAM) system. DREAM currently operates dust forecasts over the Mediterranean region (http://www.bsc.es/projects/earthscience/DREAM/) considering four particle size bins while only the first two are relevant for long‐range transport analysis since their life time is larger than 12 hours. A more detailed bin method is implemented, and two different dust distributions at sources are compared to the operational version. Evaluations are performed at two wavelengths (532 and 1064 nm). The dust horizontal and vertical structure simulated by DREAM shows very good qualitative agreement when compared to SeaWIFS satellite images and lidar height‐time displays over Barcelona. When evaluating the modeled aerosol optical depth (AOD) against Sun photometer data, significant improvements are achieved with the use of the new detailed bin method. In general, the model underpredicts the AOD for increasing Ångström exponents because of the influence of anthropogenic pollution in the boundary layer. In fact, the modeled AOD is highly anticorrelated with the observed Ångström exponents. Avignon shows higher influence of small anthropogenic aerosols which explains the better results of the model at the wavelength of 1064 nm over this location. The uncertainties of backscatter lidar inversions (20–30%) are in the same order of magnitude as the differences between the model experiments. Better model results are obtained when comparing to lidar because most of the anthropogenic effect is removed.
Aerosol constituents and their spatial distribution in the free troposphere of coastal Antarctic regions
Authors: Hara K. , Iwasaka Y. , Wada M. , Ihara T. , Shiba H. , Osada K. , Yamanouchi T.
Published: August 2006

Direct aerosol sampling of Antarctic aerosols was carried out in the free troposphere over Syowa (39.58°E, 69.00°S) and Mizuho (44.19°E, 70.41°S) stations in April and December 2000 for better understanding of aerosol constituents and their vertical distribution in the Antarctic troposphere. Individual aerosol particles were analyzed/observed by means of a transmission electron microscope and a scanning electron microscope equipped with an energy dispersive X‐ray spectrometer. Aerosol particles containing sulfur species (probably H2SO4) were identified as the major aerosol particles in the Antarctic free troposphere, whereas sea‐salt, mineral and anthropogenic particles were minor aerosol particles. Although H2SO4 and sea‐salt particles were observed in the free troposphere during both April and December, mineral and anthropogenic particles were distributed only in December. Sea‐salt particles show lower Cl/Na molar ratios relative to seawater because of Cl liberation. S/Na molar ratios of the particles are also low, suggesting that Cl− in the sea salt had been replaced by anions other than SO42− and CH3SO3−. The Cl liberation from sea‐salt particles in the Antarctic free troposphere might have occurred via the heterogeneous reactions mainly involving reactive nitrogen oxides.
Particle dynamics method simulations of stochastic collisions of sandy grain bed with mixed size in aeolian sand saltation
Authors: Zhou You‐He , Li Wan‐Qing , Zheng Xiao Jing
Published: August 2006

This paper presents a statistical approach to predict the behavior of liftoff grains on the basis of simulation of random collisions between incident grains and the mixed sand bed by means of the particle dynamics method (PDM). In the simulation a two‐dimensional sand bed of grain‐grain contact between the mixed size grains, which are simplified by circular disks, is stochastically generated by a random number generator and the “particle cooling” technique. After the diameter distribution of incident grains is divided into n subregions of representative diameters, first, the collisions are simulated for each representative diameter of incident grains with an incident velocity impacting the mixed sand bed, for which the information about liftoff grains may be gained at the end of collisions. After that a statistic approach is proposed to get the average values of velocity and number of the ejecting and rebounding grains as well as the probability density function (pdf) of liftoff velocity in terms of magnitude and angle. In order to guarantee steady state of the statistical quantities, 110 samples of the random collisions of each representative diameter of grains with an incident velocity but different (or random) contact position are taken in a case study in which the average diameter of the grains is the same as that of the uniform sand grains employed by Anderson and Haff (1991). The numerical results show that there are notable differences in the statistical quantities between them, and some of the results obtained here are in good agreement with the measurement data of multiple grain size. Finally, the pdf of initial velocity in terms of both magnitude and angle is derived on the basis of the simulation results.
Evaluation of space‐based constraints on global nitrogen oxide emissions with regional aircraft measurements over and downwind of eastern North America
Authors: Martin Randall V. , Sioris Christopher E. , Chance Kelly , Ryerson Thomas B. , Bertram Timothy H. , Wooldridge Paul J. , Cohen Ronald C. , Neuman J. Andy , Swanson Aaron , Flocke Frank M.
Published: August 2006

We retrieve tropospheric nitrogen dioxide (NO2) columns for May 2004 to April 2005 from the SCIAMACHY satellite instrument to derive top‐down emissions of nitrogen oxides (NOx = NO + NO2) via inverse modeling with a global chemical transport model (GEOS‐Chem). Simulated NO2 vertical profiles used in the retrieval are evaluated with airborne measurements over and downwind of North America (ICARTT); a northern midlatitude lightning source of 1.6 Tg N yr−1 minimizes bias in the retrieval. Retrieved NO2 columns are validated (r2 = 0.60, slope = 0.82) with coincident airborne in situ measurements. The top‐down emissions are combined with a priori information from a bottom‐up emission inventory with error weighting to achieve an improved a posteriori estimate of the global distribution of surface NOx emissions. Our a posteriori NOx emission inventory for land surface NOx emissions (46.1 Tg N yr−1) is 22% larger than the GEIA‐based a priori bottom‐up inventory for 1998, a difference that reflects rising anthropogenic emissions, especially from East Asia. A posteriori NOx emissions for East Asia (9.8 Tg N yr−1) exceed those from other continents. The a posteriori inventory improves the GEOS‐Chem simulation of NOx, peroxyacetylnitrate, and nitric acid with respect to airborne in situ measurements over and downwind of New York City. The a posteriori is 7% larger than the EDGAR 3.2FT2000 global inventory, 3% larger than the NEI99 inventory for the United States, and 68% larger than a regional inventory for 2000 for eastern Asia. SCIAMACHY NO2 columns over the North Atlantic show a weak plume from lightning NOx.
Observation of a fast ozone loss in the marginal ice zone of the Arctic Ocean
Authors: Jacobi Hans‐Werner , Kaleschke Lars , Richter Andreas , Rozanov Alexei , Burrows John P.
Published: August 2006

In both polar regions tropospheric ozone regularly decreases during springtime to negligible concentrations in the atmospheric boundary layer. Here we report the observation of a dramatic ozone depletion event in the atmospheric boundary layer in the vicinity of new ice fields in the marginal ice zone (MIZ) of the Arctic Ocean monitored by instrumentation on board the icebreaker RV Polarstern. The ozone mixing ratio decreased from approximately 40 to below 1 ppbV in less than 7 hours. The analyses of backward trajectories and the synoptic conditions indicate that the observed decrease was not caused by the transport of ozone‐free air, but that the ozone depletion occurred locally. Accordingly, bromine oxide, which is formed during the photochemical destruction of ozone in the presence of reactive bromine compounds, was significantly enhanced: Bromine oxide concentrations of approximately 1.8 · 109 molecules cm−3 are retrieved around the same location from SCIAMACHY satellite observations assuming a uniform vertical distribution within the boundary layer. The release of bromine in the MIZ where the new ice formation took place appears to be the most likely explanation for the activation of reactive bromine compounds and subsequent depletion of ozone. Since the conditions were favorable for the formation of frost flowers, we suggest that these are the most likely sources of the reactive bromine. However, contributions of heterogeneous reactions on other surfaces like the highly saline brine on the new ice, aerosols generated from frost flowers, and sea salt aerosols deposited on the snowpack on top of the sea ice cannot be ruled out.
Enhanced vertical transport efficiency of aerosol in convective clouds due to increases in tropospheric aerosol abundance
Authors: Cui Zhiqiang , Carslaw Kenneth S.
Published: August 2006

A numerical model is used to show that decreases in the precipitation efficiency of a midlatitude continental convective cloud in response to increases in aerosol concentration can significantly affect the efficiency with which aerosol is transported from the lower to the upper troposphere (UT). We use a 2‐D nonhydrostatic cloud and aerosol microphysics model to show that a moderately deep mixed phase convective cloud can significantly perturb aerosol in the UT: The cloud causes an increase in UT aerosol mass when the initial UT aerosol abundance is low and a decrease when the initial UT abundance is high. Realistic increases in cloud condensation nucleus (CCN) concentrations reduce the precipitation efficiency and thereby the scavenging efficiency of aerosol and allow more aerosol material to be transported to the UT. The enhancement of the UT aerosol mass after a cloud event therefore increases in clouds with higher CCN concentration, a positive feedback driven by the response of scavenging rates to aerosol abundance. Convective clouds are the principal mechanism by which lower tropospheric aerosol material is transported into the UT. The enhancement in the efficiency of this transport in high aerosol conditions may mean that in some locations, UT aerosol will be particularly sensitive to the aerosol content of the lower troposphere.
Statistical conditional simulation of a multiresolution numerical air quality model
Authors: Shao X. , Stein M. L.
Published: August 2006

This paper addresses subgrid variability, an issue that naturally arises in multiresolution numerical air quality models. Unlike previous approaches, which fit a parametric distribution over a spatial block and perform the fit from block to block independently over space and time, our approach to dealing with the subgrid variability is to describe the space‐time conditional distribution of high‐resolution output given its low‐resolution counterpart. A novel conditional simulation approach is proposed to produce an ensemble of high‐resolution runs based on the runs we have, and various criteria are used to assess whether our simulated high‐resolution runs capture the overall space‐time variability of the original high‐resolution runs. The main idea of our algorithm is to apply a nonlinear filter to the high‐resolution runs based on the low‐resolution runs and then perform a time domain block bootstrap for the residuals simultaneously over space. The algorithm proposed in this paper can be readily used by practitioners to generate random high‐resolution runs as a useful surrogate to the real high‐resolution runs when one has low‐resolution runs for a long period and only a few days' high‐resolution runs.
Monitoring the generation and propagation of ionospheric disturbances and effects on Global Navigation Satellite System positioning
Authors: Stankov S. M. , Jakowski N. , Tsybulya K. , Wilken V.
Published: August 2006

To gain a more comprehensive view of the powerful and dynamic plasma processes occurring during ionospheric storms, ground‐ and space‐based observations using Global Navigation Satellite System (GNSS) signals have been analyzed. Several case and statistical studies of ionospheric storms are presented, clearly showing the generation and propagation of ionospheric disturbances. Discussed are the capabilities of advanced techniques for routine monitoring of the ionosphere and studying the ionospheric perturbations. It is concluded that the permanent monitoring of the ionosphere‐plasmasphere system can play a significant role in mitigating adverse space weather effects on GNSS‐based positioning.