bluuebunny/crossref_metadata_2025 huggingface dataset:
Die mehrfeldrige Spannbandbrücke Slinky Springs to Fame in Oberhausen
Authors: Schlaich Mike , Goldack Arndt , Nier Mathias
Published: February 2012

Essen wurde im Jahr 2010 Europäische Kulturhauptstadt, und zu diesem Anlass wurde der Künstler Tobias Rehberger eingeladen, eine Skulptur über den Rhein‐Herne‐Kanal zu gestalten, die gleichzeitig Brückenfunktion übernehmen sollte. Für die früh ins Planungsteam gerufenen Bauingenieure ergab sich so die Möglichkeit, in der eher seltenen Konstellation Künstler‐Bauingenieur das Brücken‐Gesamtkunstwerk anzugehen: gute Kunst und gutes Tragwerk. Das Resultat, die Brückenskulptur Slinky Springs to Fame, ist eine leichte, mehrfeldrige und sehr farbenfrohe Spannbandbrücke, die, von einer Spirale umwickelt, den Rhein‐Herne‐Kanal in Oberhausen überspannt. In diesem Beitrag werden Entwurf, Konstruktion und Bau dieser Brücke sowie ihre dynamischen Besonderheiten beschrieben.

The multi‐span stress ribbon bridge called Slinky Springs to Fame in Oberhausen, Germany. The city of Essen became European Capital of Culture in 2010. For this reason, the artist Tobias Rehberger was invited to design a sculpture across the Rhein‐Herne‐Canal, which also should enable people to cross the canal. The structural engineers, who could join the team at an early design stage, had the opportunity to strive within the relation artist – structural engineer for a synthesis: good art and good structure. The result, the bridge sculpture Slinky Springs to Fame, is a lightweight and very colourful stress ribbon bridge crossing the Rhein‐Herne‐Canal, which is wrapped by a spiral. This paper describes in detail the conceptual and structural design as well as dynamic aspects and the construction of the bridge.
Physical–chemical, thermal, and functional properties of achira (Canna indica L.) flour and starch from different geographical origin
Authors: Andrade‐Mahecha Margarita M. , Tapia‐Blácido Delia R. , Menegalli Florencia C.
Published: February 2012

Achira (Canna indica L.) is a plant native to the Andes in South America, a starchy source, and its cultivation has expanded to different tropical countries, like Brazil. In order to evaluate the potential of this species, starch and flours with different particle size were obtained from Brazilian achira rhizomes. Proximal analyses, size distribution, SEM, swelling power, solubility, DSC, XRD analysis, and FTIR were performed for characterization of these materials. Flours showed high dietary fiber content (16.5–32.2% db) and high concentration of starch in the case of the smaller particle size fraction. Significant differences in protein and starch content, swelling power, solubility, and thermal properties were observed between the Brazilian and the Colombian starch. All the studied materials displayed the B‐type XRD pattern with relative crystallinity of 20.1% for the flour and between 27.0 and 28.0% for the starches. Results showed that the starch and flour produced from achira rhizomes have great technological potential for use as functional ingredient in the food industry.
Seismic performance evaluation of staggered wall system structures with middle corridors
Authors: Lee Joonho , Kang Hyungoo , Kim Jinkoo
Published: February 2012

In this paper, the seismic performance of reinforced concrete (RC) staggered wall structures with middle corridor was evaluated. To this end, 6‐, 12‐ and 18‐storey structural models were designed and were analyzed to investigate the seismic load‐resisting capacity. The response modification factors were computed based on the overstrength and the ductility capacities obtained from pushover curves. The effect of a few retrofit schemes on the enhancement of strength and ductility was also investigated. The pushover analysis results showed that the response modification factors ranged between about 4.0 and 6.0 with the average value around 5.0. When the bending rigidity of the link beams increased up to 100%, the overall overstrength increased by only about 25%. When the rebar ratio of the link beams was increased by 50%, the overstrength increased by about 40%. The replacement of the RC link beams with steel box beams resulted in superior performance of the structures with reduced beam depth. The displacement time histories of the model structures subjected to the earthquake ground motions scaled to the design seismic load showed that the maximum interstorey drifts were well below the limit state specified in the design code. Based on the analysis results, it was concluded that the staggered wall systems with a middle corridor had enough capacity to resist the design seismic load. Copyright © 2012 John Wiley & Sons, Ltd.
High‐intensity focused ultrasound treatment for twin reversed arterial perfusion sequence
Authors: Ichizuka K. , Hasegawa J. , Nakamura M. , Matsuoka R. , Sekizawa A. , Okai T. , Umemura S.
Published: February 2012

Twin reversed arterial perfusion (TRAP) sequence is a serious complication of monochorionic twin pregnancies, in which arterioarterial anastomoses allow blood flow from a ‘pump’ fetus to an acardiac fetus via reversed flow in the latter's umbilical artery. Several trial treatments for TRAP sequence have been reported, but all of these have been invasive. We present a case of TRAP sequence in which high‐intensity focused ultrasound (HIFU) was applied to the umbilical artery of the anomalous twin at 26 weeks as a non‐invasive fetal therapy. The HIFU intensity was set at approximately 2300 W/cm2 with exposure periods of 10 s. Color Doppler ultrasound showed a decrease in blood supply to the anomalous twin, although complete occlusion of the targeted vessel was not achieved. Delivery was by Cesarean section at 29 weeks' gestation and the pump twin survived, without severe clinical complications at 6 months. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.
Prefrontal space ratio: comparison between trisomy 21 and euploid fetuses in the second trimester
Authors: Sonek J. , Molina F. , Hiett A. K. , Glover M. , McKenna D. , Nicolaides K. H.
Published: February 2012

Objective

To evaluate a novel ultrasound measurement, the prefrontal space ratio (PFSR), in second‐trimester trisomy 21 and euploid fetuses.

Methods

Stored three‐dimensional volumes of fetal profiles from 26 trisomy 21 fetuses and 90 euploid fetuses at 15–25 weeks' gestation were examined. A line was drawn between the leading edge of the mandible and the maxilla (MM line) and extended in front of the forehead. The ratio of the distance between the leading edge of the skull and that of the skin (d1) to the distance between the skin and the point where the MM line was intercepted (d2) was calculated (d2/d1). The distributions of PFSR in trisomy 21 and euploid fetuses were compared, and the relationship with gestational age in each group was evaluated by Spearman's rank correlation coefficient (rs).

Results

The PFSR in trisomy 21 fetuses (mean, 0.36; range, 0–0.81) was significantly lower than in euploid fetuses (mean, 1.48; range, 0.85–2.95; P < 0.001 (Mann–Whitney U‐test)). There was no significant association between PFSR and gestational age in either trisomy 21 (rs = 0.25; 95% CI, − 0.15 to 0.58) or euploid (rs = 0.06; 95% CI, − 0.15 to 0.27) fetuses.

Conclusion

The PFSR appears to be a highly sensitive and specific marker of trisomy 21 in the second trimester of pregnancy. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.
Radiofrequency ablation vs bipolar umbilical cord coagulation in the management of complicated monochorionic pregnancies
Authors: Bebbington M. W. , Danzer E. , Moldenhauer J. , Khalek N. , Johnson M. P.
Published: February 2012

Objective

The application of radiofrequency ablation (RFA) termination procedures to complicated cases involving monochorionic twins offers the potential of a less invasive option when compared to endoscopic techniques. The purpose of this study was to compare outcomes between these two techniques.

Methods

A retrospective review was undertaken of all cases of complicated monochorionic twin gestations treated at the Children's Hospital of Philadelphia from July 1996 to December 2010. Cases were identified from the fetal treatment database and data extracted in a uniform fashion from the patients' charts.

Results

A total of 149 cases were identified with procedures performed on 146. Indications for selective termination of one fetus were twin reversed arterial perfusion sequence in 53, severe twin‐to‐twin transfusion syndrome in 43, discordance for fetal anomalies in 26 and selective intrauterine growth restriction in 24. Eighty‐eight cases were managed with bipolar cord coagulation (BCC) and 58 with RFA. The procedures in all cases were technically successful in achieving selective termination. The mean gestational age at the time of the procedure was 20.9 ± 2.7 weeks in the BCC group vs 20.2 ± 2.2 weeks in the RFA group (P = 0.1). The median gestational age at delivery was 34.7 (interquartile range (IQR), 29.2–38.6) weeks for the BCC group vs 33.0 (IQR, 23.4–38.9) weeks in the RFA group (P = 0.073). Mean birth weight did not differ between the two groups. The procedure‐to‐delivery time was 87.1 ± 42.1 days for the BCC group vs 73.8 ± 47.2 days for the RFA group (P = 0.1). Overall survival was 85.2% in the BCC group vs 70.7% in the RFA group (P = 0.014). This was attributed primarily to a survival rate of 10.5% in the RFA group compared with 31.6% in the BCC group for cases where delivery occurred before 28 weeks' gestation (P = 0.01). Premature rupture of the membranes occurred in 27.3% in the BCC group vs 13.7% in the RFA group (P = 0.05). Preterm labor was more common in the BCC group than in the RFA group (22.4 vs 7%, respectively; P = 0.009).

Conclusion

Despite the smaller caliber of the instrument, RFA is not associated with a decrease in the overall complication rate for selective termination procedures. The technique used for selective termination should still be determined by technical considerations but patients should be informed of the survival rate associated with each technique. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.
Kinetics of the Transesterification of Castor Oil with Maleic Anhydride Using Conventional and Microwave Heating
Authors: Mazo Paula , Estenoz Diana , Sponton Marisa , Rios Luis
Published: February 2012

The transesterification of castor oil with maleic anhydride was studied using conventional and microwave heating. Reactions were followed by measuring the acid value and the reaction products were characterized by FTIR and 1H NMR. A kinetic model that fit the experimental data was derived. The transesterification was non‐catalytic and first‐order with respect to each reactant. Non‐thermal effects of microwaves were not observed. Activation energy, enthalpy of activation, entropy of activation and free energy of activation were similar regardless of the heating method. Rate constants and the pre‐exponential factor were lower with the use of microwave heating, which could be a consequence of the decrease in the dielectric constant of the reaction liquid as the reaction progresses.
Increasing Stearidonic Acid (SDA) in Modified Soybean Oil by Lipase‐Mediated Acidolysis
Authors: Kleiner Leslie , Vázquez Luis , Akoh Casimir C.
Published: February 2012

The objective of this work was to synthesize a structured lipid (SL) enriched in stearidonic acid (SDA, C18:4 ω‐3), from modified soybean oil (MSO) originally containing ~25% SDA. Low temperature crystallization (LTC) of MSO triacylglycerols (TAG) and free fatty acids (FFA) was performed. The TAG and FFA crystallization products (LTC‐TAG and LTC‐FFA, respectively) had SDA contents of 48.72 and 60.78%, respectively. Enzymatic acidolysis between MSO and LTC‐FFA was studied utilizing Novozym 435 and Lipozyme TL IM as biocatalysts. Substrate molar ratio, incubation time, solvent, and enzyme load were explored. Equilibrium was reached at 96 and 48 h for Novozym 435 and Lipozyme TL IM‐catalyzed reactions, respectively. The best conditions from these studies were also applied to the acidolysis of LTC‐TAG and LTC‐FFA. Utilizing Lipozyme TL IM and solvent free conditions, SLs with SDA contents of 37.61 ± 1.00% (20.86 ± 6.48% at sn‐2 position) and 53.46 ± 1.85% SDA (36.37 ± 3.14% at sn‐2 position) were obtained from the acidolysis reaction between MSO and LTC‐FFA, and LTC‐TAG and LTC‐FFA, respectively. Compared to the original SDA content of MSO, this process leads to a 52 and 116% increase in SDA content, respectively.
Timing analysis of leader-based and decentralized Byzantine consensus algorithms
Authors: Borran Fatemeh , Hutle Martin , Schiper André
Published: February 2012

We consider the Byzantine consensus problem in a partially synchronous system with strong validity. For this problem, two main algorithms—with different resilience—are described in the literature. These two algorithms assume a leader process. A decentralized variant (variant without leader) of these two algorithms has also been given in a previous paper. Here, we compare analytically, in a round-based model, the leader-based variant of these algorithms with the decentralized variant. We show that, in most cases, the decentralized variant of the algorithm has a better worst-case execution time. Moreover, for the practically relevant case t≤2 (where t is the maximum number of Byzantine processes), this worst-case execution time is even at least as good as the execution time of the leader-based algorithms in fault-free runs.
An exception handling system for service component architectures
Authors: Castor Fernando , Leite Douglas Siqueira , Rubira Cecília Mary F.
Published: February 2012

The Service Component Architecture (SCA) makes it possible to combine existing and new services based on a variety of technologies with components built using a component-based development approach. However, when asynchronous service compositions are executed, one or more errors can occur, possibly at the same time, affecting the dependability of the composition. To guarantee that the composition succeeds or at least fails in a controlled manner, fault tolerance mechanisms must be employed. In this paper, we propose a novel exception handling model that targets the needs of dependable SCA applications. The model is applicable to service-oriented systems and allows the creation of fault-tolerant asynchronous service compositions. The EH-SCA framework instantiates the proposed model as an extension of the Apache Tuscany SCA infrastructure. Developers can apply this instantiation of the model to both new and existing applications by using a simple and flexible aspect-oriented programming model. Finally, a case study of the EH-SCA framework shows how it can be used to build dependable distributed applications.
ATX and LPA receptor 3 are coordinately up‐regulated in lipopolysaccharide‐stimulated THP‐1 cells through PKR and SPK1‐mediated pathways
Authors: Li Song , Xiong Chaoyang , Zhang Junjie
Published: February 2012

Lysophosphatidic acid (LPA) is an important phospholipid mediator in inflammation and immunity. Previously, we showed that autotaxin (ATX), the enzyme producing LPA from lysophosphatidylcholine (LPC), is induced by LPS in THP‐1 cells via the activation of PKR, JNK and p38 MAPK. In this study, we find that ATX and LPA receptor 3 (LPA3) are coordinately up‐regulated in LPS‐stimulated THP‐1 cells. PKR‐mediated activation of JNK1 and p38 MAPK is required for both ATX and LPA3 up‐regulation. SPK1‐mediated activation of the PI3K‐AKT‐β‐catenin pathway is essential for ATX induction, while SPK1‐mediated ERK activation is required for LPA3 up‐regulation. Either ATX or LPA3 knockdown inhibited CCL8 induction by LPS, suggesting that ATX and LPA3 are involved in CCL8 induction during the inflammatory process against bacterial infection.
Insights into differential modulation of receptor function by hinge region using novel agonistic lutropin receptor and inverse agonistic thyrotropin receptor antibodies
Authors: Majumdar Ritankar , Railkar Reema , Dighe Rajan R
Published: February 2012

We report two antibodies, scFv 13B1 and MAb PD1.37, against the hinge regions of LHR and TSHR, respectively, which have similar epitopes but different effects on receptor function. While neither of them affected hormone binding, with marginal effects on hormone response, scFv 13B1 stimulated LHR in a dose‐dependent manner, whereas MAb PD1.37 acted as an inverse agonist of TSHR. Moreover, PD1.37 could decrease the basal activity of hinge region CAMs, but had varied effects on those present in ECLs, whereas 13B1 was refractory to any CAMs in LHR. Using truncation mutants and peptide phage display, we compared the differential roles of the hinge region cysteine box‐2/3 as well as the exoloops in the activation of these two homologus receptors.
Construction of synthetic regulatory networks in yeast
Authors: Blount Benjamin A. , Weenink Tim , Ellis Tom
Published: February 2012

Yeast species such as Saccharomyces cerevisiae have been exploited by humans for millennia and so it is therefore unsurprising that they are attractive cells to re‐engineer for industrial use. Despite many beneficial traits yeast has for synthetic biology, it currently lags behind Escherichia coli in the number of synthetic networks that have been described. While the eukaryotic nature of yeast means that its regulation is not as simple to predict as it is for E. coli, once initial considerations have been made yeast is pleasingly tractable. In this review we provide a loose guide for constructing and implementing synthetic regulatory networks in S. cerevisiae using examples from previous research to highlight available resources, specific considerations and potential future advances.
Two sides of the story? Smad4 loss in pancreatic cancer versus head‐and‐neck cancer
Authors: Malkoski Stephen P. , Wang Xiao-Jing
Published: February 2012

TGFβ signaling Smads (Smad2, 3, and 4) were suspected tumor suppressors soon after their discovery. Nearly two decades of research confirmed this role and revealed other divergent and cancer‐specific functions including paradoxical tumor promotion effects. Although Smad4 is the most potent tumor suppressor, its functions are highly context‐specific as exemplified by pancreatic cancer and head‐and‐neck cancer: in pancreatic cancer, Smad4 loss cannot initiate tumor formation but promotes metastases while in head‐and‐neck cancer Smad4 loss promotes cancer progression but also initiates tumor formation, likely through effects on genomic instability. The differing consequences of impaired Smad signaling in human cancers and the molecular mechanisms that underpin these differences will have important implications for the design and application of novel targeted therapies.
Perinatal lead exposure alters postnatal cholinergic and aminergic system in rat brain: reversal effect of calcium co‐administration
Authors: Basha D. Chand , Rani M. Usha , Devi C. Bhuvaneswari , Kumar M. Ram , Reddy G. Rajarami
Published: February 2012

Our earlier studies indicated the role of neurotransmitter systems in lead (Pb) induced behavioral perturbations. In this study, we examined the alterations in synaptosomal acetylcholine (ACh), epinephrine, dopamine, acetylcholinesterase (AChE), and mitochondrial monoamine oxidase (MAO) in the cerebellum and hippocampus of perinatally Pb‐exposed rats. Rats (Wistar) were exposed to 0.2% Pb (Pb acetate in drinking water of mother) from gestational day 6 and the pups were exposed lactationally (through mother's milk) to Pb till weaning (postnatal day 21). Studies conducted on different postnatal days (PND 21, 28, 35 and 60) showed significant decreases in synaptosomal AChE and mitochondrial MAO activities, and increases in the levels of ACh, dopamine and epinephrine in the cerebellum and hippocampus of Pb‐exposed rats. These alterations were greater at PND 35 and more pronounced in the cholinergic system (ACh and AChE) of hippocampus and the aminergic system (epinephrine, dopamine and MAO) of cerebellum. The total locomotor activity and exploratory behavior were also decreased significantly in Pb‐exposed animals corresponding to the alterations observed in cholinergic and aminergic systems. Calcium administration together with Pb, however significantly reversed the Pb‐induced alterations in transmitters and enzymes, as well as exploratory and motor behavior suggesting protective effect of calcium in Pb‐exposed animals.
Neonatal handling affects learning, reversal learning and antioxidant enzymes activities in a sex‐specific manner in rats
Authors: Noschang Cristie , Krolow Rachel , Arcego Danusa Mar , Toniazzo Ana Paula , Huffell Ana Paula , Dalmaz Carla
Published: February 2012

Early life experiences have profound influences on behavior and neurochemical parameters in adult life. The aim of this study is to verify neonatal handling‐induced sex specific differences on learning and reversal learning as well as oxidative stress parameters in the prefrontal cortex and striatum of adult rats. Litters of rats were non‐handled or handled (10 min/day, days 1–10 after birth). In adulthood, learning and reversal learning were evaluated using a Y maze associated with palatable food in male and female rats. Morris water maze reversal learning was verified in males. Oxidative stress parameters were evaluated in both genders. Male neonatal handled animals had a worse performance in the Y maze reversal learning compared to non‐handled ones and no difference was observed in the water maze reversal learning task. Regarding females, neonatal handled rats had a better performance during the Y maze learning phase compared to non‐handled ones. In addition, neonatal handled female animals showed a decreased SOD/CAT ratio in the PFC compared to non‐handled females. We conclude that neonatal handling effects on learning and memory in adult rats are sex and task specific. The sex specific differences are also observed in the evaluation of antioxidant enzymes activities with neonatal handling affecting only females.
The Reproducibility of Berg Balance Scale and the Single‐Leg Stance in Chronic Stroke and the Relationship Between the Two Tests
Authors: Flansbjer Ulla‐Britt , Blom Johanna , Brogårdh Christina
Published: February 2012

Objective

To assess the reproducibility of the Berg Balance Scale (BBS) and the Single‐leg Stance (SLS), and the validity of the SLS as an independent test of upright postural control in patients with chronic stroke.

Design

An intra‐rater test–retest reproducibility study. The BBS and the SLS were assessed twice, 7 days apart.

Setting

A university hospital.

Participants

Fifty individuals; 6‐46 months after a stroke.

Main Outcome Measurements

The reproducibility of the BBS and the SLS was evaluated with intraclass correlation coefficient (ICC2,1), the mean difference between the 2 test sessions (d̄) with 95% confidence interval (95% CI), the standard error of measurement (standard error of measurement [SEM]%), the smallest real difference (SRD%), and the Bland‐Altman graphs. To assess validity of SLS, the relationship between the SLS and the BBS was analyzed by the Pearson correlation coefficient.

Results

The ICC2,1 was 0.88 for the BBS, and the ICC2,1 values were 0.88 for the nonparetic limb and 0.92 for the paretic lower limb for the SLS. The smallest change that indicates a real improvement for a group of individuals, SEM%, was 3% for BBS, 15% for the nonparetic limb and 27% for the paretic limb for SLS. The smallest real difference for a single individual was 8% for BBS but was higher for SLS, at 42% for the nonparetic limb, and 74% for the paretic limb. There was a significant relationship between the SLS and the BBS (r = 0.65‐0.79; P < .001).

Conclusions

The BBS and the SLS are reproducible measurements in patients with chronic stroke, but only the BBS is sensitive enough to follow changes over time or after an intervention. The SLS is strongly related to the BBS and can be used as an independent test to measure upright postural control after a stroke.
C-start: optimal start of larval fish
Authors: Gazzola M. , Van Rees W. M. , Koumoutsakos P.
Published: February 2012

We investigate the C-start escape response of larval fish by combining flow simulations using remeshed vortex methods with an evolutionary optimization. We test the hypothesis of the optimality of C-start of larval fish by simulations of larval-shaped, two- and three-dimensional self-propelled swimmers. We optimize for the distance travelled by the swimmer during its initial bout, bounding the shape deformation based on the larval mid-line curvature values observed experimentally. The best motions identified within these bounds are in good agreement within vivoexperiments and show that C-starts do indeed maximize escape distances. Furthermore we found that motions with curvatures beyond the ones experimentally observed for larval fish may result in even larger escape distances. We analyse the flow field and find that the effectiveness of the C-start escape relies on the ability of pronounced C-bent body configurations to trap and accelerate large volumes of fluid, which in turn correlates with large accelerations of the swimmer.
Quality, and not Just Quantity, of Education Accounts for Differences in Psychometric Performance between African Americans and White Non-Hispanics with Alzheimer's Disease
Authors: Chin Alexander L. , Negash Selam , Xie Sharon , Arnold Steven E. , Hamilton Roy
Published: February 2012

The effect of race on cognitive test performance in the evaluation of Alzheimer's disease (AD) remains controversial. One factor that may contribute substantially to differences in cognitive test performance in diverse populations is education. The current study examined the extent to which quality of education, even after controlling for formal years of education, accounts for differences in cognitive performance between African Americans and White Non-Hispanics (WNHs). The retrospective cohort included 244 patients diagnosed with AD who self-identified as African Americans (n= 51) or WNHs (n= 193). The Wechsler Test of Adult Reading (WTAR) was used as an estimate of quality of education. In an analysis that controlled for traditional demographics, including age, sex, and years of formal education, African Americans scored significantly lower than WNHs on the Mini-Mental State Examination, as well as on neuropsychological tests of memory, attention, and language. However, after also adjusting for reading level, all previously observed differences were significantly attenuated. The attenuating effect remained even after controlling for disease severity, indicating that reading scores are not confounded by severity of dementia. These findings suggest that quality, and not just quantity, of education needs to be taken into account when assessing cognitive performance in African Americans with AD. (JINS, 2012,18, 277–285)
The poverty implications of high oil prices in South Africa
Authors: Chitiga Margaret , Fofana Ismael , Mabugu Ramos
Published: February 2012

An energy-focused macro-micro approach is used to assess the poverty implications of government policy response to increases in international oil prices in South Africa. The first scenario assumes that increases in international oil prices are passed on to end users with no changes in government policy instruments. In this scenario, poverty indicators increase. The second scenario assumes that the world price increases are nullified by a price subsidy by the government. This scenario still leads to an increase in poverty as the beneficial price effect is cancelled out by a decline in households’ income induced by the financing method used. While revenue generated from a 50 per cent tax on windfall profit of the petroleum industry helps to minimize the loss in government revenue, it does not contribute to mitigating the increasing poverty trend, since the decline in saving and investment under this scenario restricts the country's growth, employment and income distribution perspectives.
Characterization of Micro- and Nanophase Separation of Dentin Bonding Agents by Stereoscopy and Atomic Force Microscopy
Authors: Toledano Manuel , Yamauti Monica , Osorio Estrella , Monticelli Francesca , Osorio Raquel
Published: February 2012

The aim was to study the effect of solvents on the phase separation of four commercial dental adhesives. Four materials were tested: ClearfilTM SE Bond (CSE), Clearfil Protect Bond (CPB), Clearfil S3 Bond (CS3), and One-Up Bond F Plus (OUB). Distilled water or ethanol was used as a solvent (30 vol%) for microphase separation studies, by stereoscopy. For nanophase images, the mixtures were formulated with two different solvent concentrations (2.5 versus 5 vol%) and observed by atomic force microscopy. Images were analyzed by using MacBiophotonics ImageJ to measure the area of bright domains. Macrophase separations, identified as a loss of clarity, were only observed after mixing the adhesives with water. Nanophase separations were detected with all adhesive combinations. The area of bright domains ranged from 132 to 1,145 nm2 for CSE, from 15 to 285 nm2 for CPB, from 149 to 380 nm2 for CS3, and from 26 to 157 nm2 for OUB. In water-resins mixtures, CPB was the most homogeneous and OUB showed the most heterogeneous phase formation. In ethanol-resin mixtures, CSE attained the most homogeneous structure and OUB showed the most heterogeneous phase. Addition of 5 vol% ethanol to resins decreased the nanophase separation when compared with the control materials.
Molecular mechanisms underlying chemical liver injury
Authors: Gu Xinsheng , Manautou Jose E.
Published: February 2012

The liver is necessary for survival. Its strategic localisation, blood flow and prominent role in the metabolism of xenobiotics render this organ particularly susceptible to injury by chemicals to which we are ubiquitously exposed. The pathogenesis of most chemical-induced liver injuries is initiated by the metabolic conversion of chemicals into reactive intermediate species, such as electrophilic compounds or free radicals, which can potentially alter the structure and function of cellular macromolecules. Many reactive intermediate species can produce oxidative stress, which can be equally detrimental to the cell. When protective defences are overwhelmed by excess toxicant insult, the effects of reactive intermediate species lead to deregulation of cell signalling pathways and dysfunction of biomolecules, leading to failure of target organelles and eventual cell death. A myriad of genetic factors determine the susceptibility of specific individuals to chemical-induced liver injury. Environmental factors, lifestyle choices and pre-existing pathological conditions also have roles in the pathogenesis of chemical liver injury. Research aimed at elucidating the molecular mechanism of the pathogenesis of chemical-induced liver diseases is fundamental for preventing or devising new modalities of treatment for liver injury by chemicals.
Misestimation of Reliability Using Coefficient Alpha and Structural Equation Modeling When Assumptions of Tau-Equivalence and Uncorrelated Errors Are Violated
Authors: Gu Fei , Little Todd D. , Kingston Neal M.
Published: February 2012

Coefficient alpha (α) has been described as a lower bound for test reliability. However, previous research indicates that when certain assumptions are violated, α can either overestimate or underestimate reliability. Raykov (1997a) has shown how structural equation modeling (SEM) can be used to estimate reliability. This study has introduced method factors into the model in Raykov (1997a) to avoid a potential limitation of the SEM approach. Monte Carlo simulation shows that when certain assumptions are violated, either method (α or SEM) can show a substantial bias, though in the most extreme circumstances the bias of α estimates are larger than the bias of SEM-based reliability estimates. Circumstances that favor one method or the other are described and explored.
Asymmetric seasonal temperature trends
Authors: Cohen Judah L. , Furtado Jason C. , Barlow Mathew , Alexeev Vladimir A. , Cherry Jessica E.
Published: February 2012

Current consensus on global climate change predicts warming trends driven by anthropogenic forcing, with maximum temperature changes projected in the Northern Hemisphere (NH) high latitudes during winter. Yet, global temperature trends show little warming over the most recent decade or so. For longer time periods appropriate to the assessment of trends, however, global temperatures have experienced significant warming trends for all seasons except winter, when cooling trends exist instead across large stretches of eastern North America and northern Eurasia. Hence, the most recent lapse in global warming is a seasonal phenomenon, prevalent only in boreal winter. Additionally, we show that the largest regional contributor to global temperature trends over the past two decades is land surface temperatures in the NH extratropics. Therefore, proposed mechanisms explaining the fluctuations in global annual temperatures should address this apparent seasonal asymmetry.
On the information content of surface meteorology for downward atmospheric long‐wave radiation synthesis
Authors: Abramowitz Gab , Pouyanné Laure , Ajami Hoori
Published: February 2012

One of the key uncertainties in site‐based evaluations of land surface, hydrological or ecological models stems from the lack of availability of downward long‐wave radiation, even at observational stations where tens of other key variables are measured. State of the art techniques for its synthesis are typically functionally dependent on surface temperature, vapour pressure and some representation of cloudiness. Here we show that existing functional forms for downward long‐wave synthesis underutilise information in these key predictor variables, and that in fact cloudiness variables may be redundant. By using an empirical model at a range of sites globally, we examine the contribution of each of the predictor variables and conclude that an extremely simple empirical model may provide more defensible prediction where noa priori knowledge of site behavior exists.
Stratosphere‐troposphere coupling at inter‐decadal time scales: Implications for the North Atlantic Ocean
Authors: Manzini Elisa , Cagnazzo Chiara , Fogli Pier Giuseppe , Bellucci Alessio , Müller Wolfgang A.
Published: February 2012

Evidence of stratosphere‐troposphere coupling at inter‐decadal time scales is searched for in a 260‐year simulation performed with a climate model including a state‐of‐the‐art stratosphere. The boundary conditions of the simulation are specified according to preindustrial conditions and are kept constant from year to year. It is shown that long lasting (∼20 years) positive and negative anomalies of the northern winter stratospheric polar vortex exist in the simulation. Given that there are no externally imposed low frequency time variations, these persistent variations are due to internal dynamical processes of the modeled coupled atmosphere ocean system. By composite analysis, it is shown that the long lasting stratospheric vortex anomalies are connected through the troposphere to mean sea level pressure, surface temperature and sea ice cover anomalies. These connections are reminiscent of intra‐seasonal stratosphere–troposphere coupling. Over the ocean, the surface temperature and sea ice cover anomalies are indicative of the delayed Atlantic meridional overturning circulation response to atmospheric forcing. The latter is indeed found to be anomalously strong/weak during the long lasting positive/negative stratospheric vortex anomalies, providing evidence for a potential role of the stratosphere in decadal prediction.
Seasonal and long‐term vertical deformation in the Nepal Himalaya constrained by GPS and GRACE measurements
Authors: Fu Yuning , Freymueller Jeffrey T.
Published: February 2012

We analyze continuous GPS measurements in Nepal, southern side of the Himalaya, and compare GPS results with GRACE observations in this area. We find both GPS and GRACE show significant seasonal variations. Further comparison indicates that the observed seasonal GPS height variation and GRACE‐derived seasonal vertical displacement due to the changing hydrologic load exhibit very consistent results, for both amplitude and phase. For continuous GPS stations whose observation time span are longer than 3 years, the average WRMS reduction is ∼45% when we subtract GRACE‐derived vertical displacements from GPS observed time series. The comparison for annual amplitudes between GPS observed and GRACE‐derived seasonal displacements also shows consistent correlation. The good seasonal correlation between GPS and GRACE is due to the improved GPS processing strategies and also because of the strong seasonal hydrological variations in Nepal. Besides the seasonal signal, GRACE also indicates a long‐term mass loss in the Himalaya region, assuming no GIA effect. This mass loss therefore will lead to crustal uplift since the earth behaves as an elastic body. We model this effect and remove it from GPS observed vertical rates. With a 2D dislocation model, most GPS vertical rates, especially in the central part of Nepal, can be interpreted by interseismic strain from the Main Himalayan Thrust, and several exceptions may indicate the complexity of vertical motion in this region and some potential local effects.
Transient current pulses in rocket‐extended wires used to trigger lightning
Authors: Biagi C. J. , Uman M. A. , Hill J. D. , Rakov V. A. , Jordan D. M.
Published: February 2012

We analyze current, electric field, and optical signatures of the sudden electrical breakdown processes (precursors) that occur at the top of the upward extending, grounded, Kevlar‐covered copper wires used to artificially trigger lightning. For one launch, before the sustained upward positive leader initiated, we estimate that up to 10,000 precursors occurred (one every few hundred microseconds) with peak currents from 1 to more than 100 A. Luminosity at the wire tip was observed for 339 of 410 precursors examined in detail and, in seven cases, discharge channels developed to lengths of 3 to 8 m over times of several hundred microseconds. The measured propagation speeds of current pulses on the triggering wires were less than the speed of light, and decreased from about 2.8 × 108 m s−1 to about 2.3 × 108 m s−1with increasing wire‐top heights from about 80 m to about 340 m. The triggering wire and its grounding system are modeled as uniform transmission lines with model predictions that are consistent with the measured wire‐base precursor current signatures. The modeling shows that (1) the characteristic impedance of the triggering wire, the ratio of the propagating precursor voltage pulse to its associated current pulse, is between 600 and 800 Ω; (2) the 25 m ground rod grounding impedance for the peak precursor current is about 100 Ω, while the DC grounding resistance is 20 Ω; and (3) the current reflection coefficient at ground for peak precursor current is ∼0.9.
Methane emission from flooded forest in central Africa
Authors: Tathy J. P. , Cros B. , Delmas R. A. , Marenco A. , Servant J. , Labat M.
Published: February 2012

In this report we give results of methane flux measurement in the flooded forest zone of the Congo River basin in central Africa. Methane fluxes are measured by the static chamber method above three types of soils characterized by various water contents. High methane emission is recorded on flooded soils (4.59 × 1012 molecules/cm2/s) while methane uptake occurs in dry soil (−8.38 × 1010 molecules/cm2/s). Methane flux is also derived from variations of surface concentrations of methane related to the variations of air stability and from vertical profiles in the lower troposphere. The four methods used to determine the average methane emission from this wetland type yield compatible values. The average yearly flux is estimated at 2 to 4 × 1012 molecules/cm2/s or 45 to 90 mg/m2/d The total wetland area being about 105 km2, global methane emission from the flooded forest zone of the Congo River basin would represent 1.6 to 3.2 Tg (CH4) per year.
Precipitation chemistry in the Mayombé forest of equatorial Africa
Authors: Lacaux J. P. , Delmas R. , Kouadio G. , Cros B. , Andreae M. O.
Published: February 2012

An automatic wet‐only precipitation collector was operated in the coastal forest of equatorial Congo for a complete seasonal cycle (November 1986 to September 1987). Inorganic (Na+, K+, NH4+, Ca++, NO3−, Cl−, SO4=) and organic (HCOO−, CH3COO−) ions were determined in 169 samples which represent 51 rain events. An average precipitation pH of 4.74 based on the volume weighted of H+ was obtained. Rain from stratiform clouds showed higher acidity (pH = 4.62) than convective rainfall (pH = 4.81). This acidity results from a mixture of mineral acids (64%, of which about 42% is HNO3) and organic acids (36%). Most of the HNO3 component can be attributed to the emission of nitrogen oxides from vegetation burning. To study the influence of variation in rainwater ion concentrations resulting from the differences in atmospheric liquid water content, rainfall events were stratified based on rainfall amount into convective and stratiform events. The seasonal variation in the chemical composition of these types of rain events allowed us to compare the relative seasonal importance of the different sources (terrestrial biogenic, marine, soils, and biomass burning). Comparison between precipitation chemistry in Congo and in Amazonia shows that the African equatorial forest is influenced by local fires and savanna fires in the southern hemisphere during the dry season and by fires in the northern hemisphere during the wet season. In Amazonia, on the other hand, the influence of biomass burning on rainwater chemistry appears to occur predominantly in the dry season. Since the precipitation collector subdivides rainfall events into 10 sequential samples, we examined the evolution in chemical composition and deposition during four large convective events. The results demonstrate the washout of ions at the onset of precipitation producing higher rainwater concentrations and their dilution as the rainfall intensity increases.
Measurements of NOx and NOy concentrations and fluxes over Arctic tundra
Authors: Bakwin Peter S. , Wofsy Steven C. , Fan Song‐Miao , Fitzjarrald David R.
Published: February 2012

Measurements of the atmospheric concentrations of NO, NO2, total NOy, and O3 were made on a 12‐m tower in a tundra bog ecosystem in southwestern Alaska during the growing season (July–August) of 1988. Typical concentrations of NOx and NOy, were 10–15 pptv, and 130–200 pptv, respectively, lower than at other remote continental sites. Anthropogenic influences were small at this site during this time of year, but significant enhancements in NOx and NOy, concentrations were observed from distant biomass fires. Measurements of NOx and O3 vertical profiles, in combination with eddy correlation measurements of O3 flux (Jacob et al., this issue (b), provide an estimate of the NOx emission rate from the surface to the atmosphere, 0.13 (±0.05) × 109 molecules cm−2 s−1. Direct (eddy correlation) measurements of the flux of total NOy, were made for the first time, indicating a downward flux of NOy, at all times of day, with maximum deposition of 2.5 (±0.9) × 109 molecules cm−2 s−1 in the afternoon. Deposition of HNO3 appears to dominate the atmosphere/surface exchange of NOy. The mean dry deposition rate of NOY to the tundra was 1.8(±1.0) × 109 molecules cm−2 s−1, about half as large as the wet deposition rate of NO3− (Talbot et al., this issue). The impact of wet tundra ecosystems on regional and global atmospheric chemistry is discussed in light of these results.
Biosphere/atmosphere CO2 exchange in tundra ecosystems: Community characteristics and relationships with multispectral surface reflectance
Authors: Whiting Gary J. , Bartlett David S. , Fan Songmiao , Bakwin Peter S. , Wofsy Steven C.
Published: February 2012

The spatial and temporal patterns of many of the factors controlling CO2 exchange are related to characteristics of the vegetated surface which can potentially be monitored using multispectral remote sensors. Realization of this potential depends, in part, on an improved understanding of ecosystem processes and their relationship to variables which are accessible to remote sensing techniques. We examined these relationships using portable, climate‐controlled, instrumented enclosures to measure CO2 exchange rates in selected tundra sites near Bethel, Alaska. Rates were related to vegetation community type and climatic variables. Exchange rates in enclosures were compared to exchange measurements obtained by eddy correlation on a 12‐m micrometeorological tower. For an average light input of 37 einsteins/day during 20 midsummer days, the empirically modeled exchange rate for a representative area of vegetated tundra was 1.2 ±1.1 (95% confidence interval) g CO2 m−2 d−1. This was comparable to a tower measured exchange over the same time period of 1.1 ±1.1 (95% confidence interval) g CO2 m−2 d−1. Net exchange in response to varying light levels was compared for two major community types, wet meadow and dry upland tundra, and to the net exchange measured by the micrometeorological tower technique. Portable radiometers were used to measure the multispectral reflectance properties of the sites. These properties were then related to exchange rates with the goal of providing a quantitative foundation for the use of satellite remote sensing to monitor biosphere/atmosphere CO2 exchange in the tundra biome. The Normalized Difference Vegetation Index (NDVI) and the near‐infrared/red reflectance ratio (SR) computed from surface reflectance were strongly correlated with net CO2 exchange for both upland and wet meadow vegetation. However, the form of the relationship was distinct from measured correlations in other ecosystems, suggesting that global surveys may require adjustment for geographical differences in exchange processes.
Turbulent transports over tundra
Authors: Fitzjarrald David R. , Moore Kathleen E.
Published: February 2012

Measurements of the surface fluxes of heat, momentum, and water vapor using the eddy correlation technique were made from instruments on a 12‐m tower at a remote site in the western Alaskan tundra between July 13 and August 12, 1988. Except for advection, all of the terms in the heat and moisture balances were measured directly. Diurnal averages of the heat budget over periods of several days balance to within 5 W/m2. The observed Bowen ratio was approximately 1. Maximum values of sensible heat flux approached 150 W/m2 during midafternoon. At 0.13 m below the surface, the soil heat flux ranged from 15 to 20 W/m2. Surface exchange of heat and moisture over tundra during the summer is limited by a strong resistance to water vapor transfer from the upper soil layer through the ground cover (200 s/m). Though July 1988 was anomalously warm and dry in the region and August was close to normal temperature and rainfall, there was no appreciable difference in the canopy resistance between the periods. During the dry, sunny period at the end of July, the observed evaporation rate was 1.9 mm/d. The depth of seasonal permafrost melt in the region was between 0.3 and 0.4 m during the latter half of the growing season, and the permafrost edge at the field site descended at approximately 1.6 mm/d. There was no change in the albedo or in the analogous ratio for photosynthetically active radiation during the experimental period.