bluuebunny/crossref_metadata_2025 huggingface dataset:
What was the Deal for the Participants of the Argentine Local Currency Systems, the Redes de Trueque?
Authors: Gómez Georgina M
Published: July 2010

Local complementary currency systems (LCCSs), like the Local Exchange Trading System scheme in the English-speaking world, are one of the alternative economies organised to overcome the exclusionary aspects of the regular market economy and support those short of money. I analyse the benefits for the poor and unemployed of the Argentine variant, called Clubes de Trueque. I conclude that the Clubes de Trueque were a meeting point of social strata and gender groups. They became a market space “for us, women”, rather than a second-class market “for us, the poor”. In economic terms they facilitated the access to goods and services for the disenfranchised middle class and the unemployed, but did not correct the exclusionary mechanisms that affect the poorest of the poor. These findings suggest that LCCSs can help some low-income groups to protect and improve their lifestyles but are not a general tool for poverty reduction.
What Matters more for the Decision to Move: Jobs versus Amenities
Authors: Niedomysl Thomas , Hansen Høgni Kalsø
Published: July 2010

Highly skilled workers are increasingly recognised as a key competitive asset for regional development, and claims have been made that emphasise the importance of certain amenities for the prospects of attracting this particular group of workers. We use a recent large-scale survey to investigate the relative importance of jobs versus amenities for the decision to migrate, as perceived by the migrants themselves. The paper thereby adds important insights to the existing literature that has hitherto mainly focused on analysing the extent to which aggregate migration flows correlate with employment-related or amenity-related factors. The results show that jobs are considerably more important for the decision to move among highly educated migrants compared with migrants with lower education.
The Legitimacy and Governance of Norway's Sovereign Wealth Fund: The Ethics of Global Investment
Authors: Clark Gordon L , Monk Ashby H B
Published: July 2010

The Norwegian Government Pension Fund-Global is one of the world's largest sovereign wealth funds and is one of the most transparent institutions of its kind. It also has an explicit mission aimed at integrating long-term investment with a two-sided ethical commitment: to corporate engagement according to accepted global principles of best-practice corporate governance, and to ensuring that the fund is not associated with companies that pose a risk to global social and environmental justice. As such, the Norwegian fund has an ethical mandate—something remarkable when compared with other sovereign wealth funds. In this paper we argue that this mission is best understood in terms of procedural, rather than substantive, justice. Our argument is sustained by reference to recent work on the nature of state authority and legitimacy in democratic societies, the logic of institutional governance, and the functional integration of decision making. The paper focuses on the nature and significance of the recommendations from the advisory Council of Ethics and the exercise of powers related to standards of corporate governance. Implications are drawn for understanding the functional performance of the fund in the context of changing global financial markets.
Identified circuit in rat postrhinal cortex encodes essential information for performing specific visual shape discriminations
Authors: Zhang Guo-rong , Cao Haiyan , Kong Lingxin , O'Brien Jennifer , Baughns Andrew , Jan Mary , Zhao Hua , Wang Xiaodan , Lu Xiu-gui , Cook Robert G. , Geller Alfred I.
Published: July 2010

Learning theories hypothesize specific circuits encode essential information for performance. For simple tasks in invertebrates and mammals, the essential circuits are known, but for cognitive functions, the essential circuits remain unidentified. Here, we show that some essential information for performing a choice task is encoded in a specific circuit in a neocortical area. Rat postrhinal (POR) cortex is required for visual shape discriminations, protein kinase C (PKC) pathways mediate changes in neuronal physiology that support learning, and specific PKC genes are required for multiple learning tasks. We used direct gene transfer of a constitutively active PKC to prime a specific POR cortex circuit for learning visual shape discriminations. In the experiment, rats learned a discrimination, received gene transfer, learned new discriminations, received a small lesion that ablated ≈21% of POR cortex surrounding the gene transfer site, and were tested for performance for discriminations learned either before or after gene transfer. Lesions of the genetically targeted circuit selectively interfered with performance for discriminations learned after gene transfer. Activity-dependent gene imaging confirmed increased activity in the genetically targeted circuit during learning and showed the essential information was sparse-coded in ≈500 neurons in the lesioned area. Wild-type rats contained circuits with similar increases in activity during learning, but these circuits were located at unpredictable, different positions in POR cortex. These results establish that some essential information for performing specific visual discriminations can be encoded in a small, identified, neocortical circuit and provide a foundation for characterizing the circuit and essential information.
Hurricane-induced failure of low salinity wetlands
Authors: Howes Nick C. , FitzGerald Duncan M. , Hughes Zoe J. , Georgiou Ioannis Y. , Kulp Mark A. , Miner Michael D. , Smith Jane M. , Barras John A.
Published: July 2010

During the 2005 hurricane season, the storm surge and wave field associated with Hurricanes Katrina and Rita eroded 527 km
2
of wetlands within the Louisiana coastal plain. Low salinity wetlands were preferentially eroded, while higher salinity wetlands remained robust and largely unchanged. Here we highlight geotechnical differences between the soil profiles of high and low salinity regimes, which are controlled by vegetation and result in differential erosion. In low salinity wetlands, a weak zone (shear strength 500–1450 Pa) was observed ∼30 cm below the marsh surface, coinciding with the base of rooting. High salinity wetlands had no such zone (shear strengths > 4500 Pa) and contained deeper rooting. Storm waves during Hurricane Katrina produced shear stresses between 425–3600 Pa, sufficient to cause widespread erosion of the low salinity wetlands. Vegetation in low salinity marshes is subject to shallower rooting and is susceptible to erosion during large magnitude storms; these conditions may be exacerbated by low inorganic sediment content and high nutrient inputs. The dramatic difference in resiliency of fresh versus more saline marshes suggests that the introduction of freshwater to marshes as part of restoration efforts may therefore weaken existing wetlands rendering them vulnerable to hurricanes.
Viral G protein-coupled receptor up-regulates Angiopoietin-like 4 promoting angiogenesis and vascular permeability in Kaposi's sarcoma
Authors: Ma Tao , Jham Bruno C. , Hu Jiadi , Friedman Eitan R. , Basile John R. , Molinolo Alfredo , Sodhi Akrit , Montaner Silvia
Published: July 2010

Kaposi's sarcoma (KS) is an enigmatic vascular tumor thought to be a consequence of dysregulated expression of the human herpesvirus-8 (HHV-8 or KSHV)-encoded G protein-coupled receptor (vGPCR). Indeed, transgenic animals expressing vGPCR manifest vascular tumors histologically identical to human KS, with expression of the viral receptor limited to a few cells, suggestive of a paracrine mechanism for vGPCR tumorigenesis. Both human and vGPCR experimental KS lesions are characterized by prominent angiogenesis and vascular permeability attributed to the release of angiogenic molecules, most notably vascular endothelial growth factor. However, the relative contribution of these paracrine mediators to the angiogenic and exudative phenotype of KS lesions remains unclear. Here we show that vGPCR up-regulation of Angiopoietin-like 4 (ANGPTL4) plays a prominent role in promoting the angiogenesis and vessel permeability observed in KS. Indeed, ANGPTL4 expression is a hallmark of vGPCR experimental and human KS lesions. Inhibition of ANGPTL4 effectively blocks vGPCR promotion of the angiogenic switch and vascular leakage in vitro and tumorigenesis in vivo. These observations suggest that ANGPTL4 is a previously unrecognized target for the treatment of patients with KS. As angiogenesis and increased vessel permeability are common themes in all solid tumors, these findings may have a broad impact on our understanding and treatment of cancer.
A new family of enzymes catalyzing the first committed step of the methylerythritol 4-phosphate (MEP) pathway for isoprenoid biosynthesis in bacteria
Authors: Sangari Félix J. , Pérez-Gil Jordi , Carretero-Paulet Lorenzo , García-Lobo Juan M. , Rodríguez-Concepción Manuel
Published: July 2010

Isoprenoids are a large family of compounds with essential functions in all domains of life. Most eubacteria synthesize their isoprenoids using the methylerythritol 4-phosphate (MEP) pathway, whereas a minority uses the unrelated mevalonate pathway and only a few have both. Interestingly,
Brucella abortus
and some other bacteria that only use the MEP pathway lack deoxyxylulose 5-phosphate (DXP) reductoisomerase (DXR), the enzyme catalyzing the NADPH-dependent production of MEP from DXP in the first committed step of the pathway. Fosmidomycin, a specific competitive inhibitor of DXR, inhibited growth of
B. abortus
cells expressing the
Escherichia coli
GlpT transporter (required for fosmidomycin uptake), confirming that a DXR-like (DRL) activity exists in these bacteria. The
B. abortus
DRL protein was found to belong to a family of uncharacterized proteins similar to homoserine dehydrogenase. Subsequent experiments confirmed that DRL and DXR catalyze the same biochemical reaction. DRL homologues shown to complement a DXR-deficient
E. coli
strain grouped within the same phylogenetic clade. The scattered taxonomic distribution of sequences from the DRL clade and the occurrence of several paralogues in some bacterial strains might be the result of lateral gene transfer and lineage-specific gene duplications and/or losses, similar to that described for typical mevalonate and MEP pathway genes. These results reveal the existence of a novel class of oxidoreductases catalyzing the conversion of DXP into MEP in prokaryotic cells, underscoring the biochemical and genetic plasticity achieved by bacteria to synthesize essential compounds such as isoprenoids.
Plague outbreaks in prairie dog populations explained by percolation thresholds of alternate host abundance
Authors: Salkeld Daniel J. , Salathé Marcel , Stapp Paul , Jones James Holland
Published: July 2010

Highly lethal pathogens (e.g., hantaviruses, hendra virus, anthrax, or plague) pose unique public-health problems, because they seem to periodically flare into outbreaks before disappearing into long quiescent phases. A key element to their possible control and eradication is being able to understand where they persist in the latent phase and how to identify the conditions that result in sporadic epidemics or epizootics. In American grasslands, plague, caused by
Yersinia pestis
, exemplifies this quiescent–outbreak pattern, because it sporadically erupts in epizootics that decimate prairie dog (
Cynomys ludovicianus
) colonies, yet the causes of outbreaks and mechanisms for interepizootic persistence of this disease are poorly understood. Using field data on prairie community ecology, flea behavior, and plague-transmission biology, we find that plague can persist in prairie-dog colonies for prolonged periods, because host movement is highly spatially constrained. The abundance of an alternate host for disease vectors, the grasshopper mouse (
Onychomys leucogaster
), drives plague outbreaks by increasing the connectivity of the prairie dog hosts and therefore, permitting percolation of the disease throughout the primary host population. These results offer an alternative perspective on plague's ecology (i.e., disease transmission exacerbated by alternative hosts) and may have ramifications for plague dynamics in Asia and Africa, where a single main host has traditionally been considered to drive
Yersinia
ecology. Furthermore, abundance thresholds of alternate hosts may be a key phenomenon determining outbreaks of disease in many multihost-disease systems.
Spontaneous generation of mammalian prions
Authors: Edgeworth Julie A. , Gros Nathalie , Alden Jack , Joiner Susan , Wadsworth Jonathan D. F. , Linehan Jackie , Brandner Sebastian , Jackson Graham S. , Weissmann Charles , Collinge John
Published: July 2010

Prions are transmissible agents that cause lethal neurodegeneration in humans and other mammals. Prions bind avidly to metal surfaces such as steel wires and, when surface-bound, can initiate infection of brain or cultured cells with remarkable efficiency. While investigating the properties of metal-bound prions by using the scrapie cell assay to measure infectivity, we observed, at low frequency, positive assay results in control groups in which metal wires had been coated with uninfected mouse brain homogenate. This phenomenon proved to be reproducible in rigorous and exhaustive control experiments designed to exclude prion contamination. The infectivity generated in cell culture could be readily transferred to mice and had strain characteristics distinct from the mouse-adapted prion strains used in the laboratory. The apparent ”spontaneous generation” of prions from normal brain tissue could result if the metal surface, possibly with bound cofactors, catalyzed de novo formation of prions from normal cellular prion protein. Alternatively, if prions were naturally present in the brain at levels not detectable by conventional methods, metal surfaces might concentrate them to the extent that they become quantifiable by the scrapie cell assay.
Hollow core of Alzheimer’s A
β
42
amyloid observed by cryoEM is relevant at physiological pH
Authors: Miller Yifat , Ma Buyong , Tsai Chung-Jung , Nussinov Ruth
Published: July 2010

Recent cryoEM density maps of A
β
42
fibrils obtained at low pH revealed two protofilaments winding around a hollow core raising the question if such
tubular
structures also exist at physiological pH. Based on the cryoEM measurements and on NMR data, we probe amyloid fibril organizations corresponding to the observed cryoEM density map. Our study demonstrates that the
tubular
A
β
42
fibril models exist at both acidic and physiological pH; however, the relative populations of the polymorphic models shift with pH. At acidic pH, the hollow core model exhibits higher population than the other models; at physiological pH, although it is less populated compared to the other models, structurally, it is stable and represents 8% of the population. We observe that only models with C termini facing the external surface of the fibril retain the hollow core under acidic and physiological conditions with dimensions similar to those observed by cryoEM; on the other hand, the hydrophobic effect shrinks the
tubular
cavity in the alternative organization. The existence of the hollow core fibril at physiological pH emphasizes the need to examine toxic effects of minor oligomeric species with unique organizations.
Caulobacter
chromosome segregation is an ordered multistep process
Authors: Shebelut Conrad W. , Guberman Jonathan M. , van Teeffelen Sven , Yakhnina Anastasiya A. , Gitai Zemer
Published: July 2010

Despite its fundamental nature, bacterial chromosome segregation remains poorly understood. Viewing segregation as a single process caused multiple proposed mechanisms to appear in conflict and failed to explain how asymmetrically dividing bacteria break symmetry to move only one of their chromosomes. Here, we demonstrate that the ParA ATPase extends from one cell pole and pulls the chromosome by retracting upon association with the ParB DNA-binding protein. Surprisingly, ParA disruption has a specific effect on chromosome segregation that only perturbs the latter stages of this process. Using quantitative high-resolution imaging, we demonstrate that this specificity results from the multistep nature of chromosome translocation. We propose that
Caulobacter
chromosome segregation follows an ordered pathway of events with distinct functions and mechanisms. Initiation releases polar tethering of the origin of replication, distinction spatially differentiates the two chromosomes, and commitment irreversibly translocates the distal centromeric locus. Thus, much as eukaryotic mitosis involves a sequence of distinct subprocesses,
Caulobacter
cells also segregate their chromosomes through an orchestrated series of steps. We discuss how the multistep view of bacterial chromosome segregation can help to explain and reconcile outstanding puzzles and frame future investigation.
Conformational switch triggered by α-ketoglutarate in a halogenase of curacin A biosynthesis
Authors: Khare Dheeraj , Wang Bo , Gu Liangcai , Razelun Jamie , Sherman David H. , Gerwick William H. , Håkansson Kristina , Smith Janet L.
Published: July 2010

The CurA halogenase (Hal) catalyzes a cryptic chlorination leading to cyclopropane ring formation in the synthesis of the natural product curacin A. Hal belongs to a family of enzymes that use Fe2+, O2and α-ketoglutarate (αKG) to perform a variety of halogenation reactions in natural product biosynthesis. Crystal structures of the enzyme in five ligand states reveal strikingly different open and closed conformations dependent on αKG binding. The open form represents ligand-free enzyme, preventing substrate from entering the active site until both αKG and chloride are bound, while the closed form represents the holoenzyme with αKG and chloride coordinated to iron. Candidate amino acid residues involved in substrate recognition were identified by site-directed mutagenesis. These new structures provide direct evidence of a conformational switch driven by αKG leading to chlorination of an early pathway intermediate.
Error-free replicative bypass of thymine glycol by the combined action of DNA polymerases κ and ζ in human cells
Authors: Yoon Jung-Hoon , Bhatia Gita , Prakash Satya , Prakash Louise
Published: July 2010

Thymine glycol (Tg) is the most common DNA lesion of thymine induced by interaction with reactive oxygen species. Because of the addition of hydroxyl groups at C5 and C6 in a Tg lesion, the damaged base loses its aromatic character and becomes nonplanar; consequently, the C5 methyl group protrudes in an axial direction and that prevents the stacking of the 5′ base above the Tg lesion. Because Tg presents a severe block to continued synthesis by replicative DNA polymerases, we determine here how human cells manage to replicate through this lesion. Using a duplex plasmid system where bidirectional replication ensues from an origin of replication, we show that translesion synthesis (TLS) makes a prominent contribution to Tg bypass and that it occurs in a predominantly error-free fashion. Also, we provide evidence that Polκ and Polζ function together in promoting error-free replication through the lesion, and based on structural and biochemical information, we propose a role for Polκ at the insertion step and of Polζ at the extension step of Tg bypass. We discuss the implications of these observations and suggest that human cells have adapted the TLS machinery to function in a much more error-free fashion than could have been predicted from the intrinsic catalytic efficiencies and fidelities of TLS polymerases.
CXCR4/YY1 inhibition impairs VEGF network and angiogenesis during malignancy
Authors: de Nigris Filomena , Crudele Valeria , Giovane Alfonso , Casamassimi Amelia , Giordano Antonio , Garban Hermes J. , Cacciatore Francesco , Pentimalli Francesca , Marquez-Garban Diana C. , Petrillo Antonella , Cito Letizia , Sommese Linda , Fiore Andrea , Petrillo Mario , Siani Alfredo , Barbieri Antonio , Arra Claudio , Rengo Franco , Hayashi Toshio , Al-Omran Mohammed , Ignarro Louis J. , Napoli Claudio
Published: July 2010

Tumor growth requires neoangiogenesis. VEGF is the most potent proangiogenic factor. Dysregulation of hypoxia-inducible factor (HIF) or cytokine stimuli such as those involving the chemokine receptor 4/stromal-derived cell factor 1 (CXCR4/SDF-1) axis are the major cause of ectopic overexpression of VEGF in tumors. Although the CXCR4/SDF-1 pathway is well characterized, the transcription factors executing the effector function of this signaling are poorly understood. The multifunctional Yin Yang 1 (YY1) protein is highly expressed in different types of cancers and may regulate some cancer-related genes. The network involving CXCR4/YY1 and neoangiogenesis could play a major role in cancer progression. In this study we have shown that YY1 forms an active complex with HIF-1α at VEGF gene promoters and increases VEGF transcription and expression observed by RT-PCR, ELISA, and Western blot using two different antibodies against VEGFB. Long-term treatment with T22 peptide (a CXCR4/SDF-1 inhibitor) and YY1 silencing can reduce in vivo systemic neoangiogenesis (
P
< 0.01 and
P
< 0.05 vs. control, respectively) during metastasis. Moreover, using an in vitro angiogenesis assay, we observed that YY1 silencing led to a 60% reduction in branches (
P
< 0.01) and tube length (
P
< 0.02) and a 75% reduction in tube area (
P
< 0.001) compared with control cells. A similar reduction was observed using T22 peptide. We demonstrated that T22 peptide determines YY1 cytoplasmic accumulation by reducing its phosphorylation via down-regulation of AKT, identifying a crosstalk mechanism involving CXCR4/YY1. Thus, YY1 may represent a crucial molecular target for antiangiogenic therapy during cancer progression.
In vitro selection of structure-switching, self-reporting aptamers
Authors: Oh Seung Soo , Plakos Kory , Lou Xinhui , Xiao Yi , Soh H. Tom
Published: July 2010

We describe an innovative selection approach to generate self-reporting aptamers (SRAs) capable of converting target-binding events into fluorescence readout without requiring additional modification, optimization, or the use of DNA helper strands. These aptamers contain a DNAzyme moiety that is initially maintained in an inactive conformation. Upon binding to their target, the aptamers undergo a structural switch that activates the DNAzyme, such that the binding event can be reported through significantly enhanced fluorescence produced by a specific stacking interaction between the active-conformation DNAzyme and a small molecule dye,
N
-methylmesoporphyrin IX. We demonstrate a purely in vitro selection-based approach for obtaining SRAs that function in both buffer and complex mixtures such as blood serum; after 15 rounds of selection with a structured DNA library, we were able to isolate SRAs that possess low nanomolar affinity and strong specificity for thrombin. Given ongoing progress in the engineering and characterization of functional DNA/RNA molecules, strategies such as ours have the potential to enable rapid, efficient, and economical isolation of nucleic acid molecules with diverse functionalities.
TCR ligand density and affinity determine peripheral induction of Foxp3 in vivo
Authors: Gottschalk Rachel A. , Corse Emily , Allison James P.
Published: July 2010

T cell receptor (TCR) ligation is required for the extrathymic differentiation of forkhead box p3+ (Foxp3+) regulatory T cells. Several lines of evidence indicate that weak TCR stimulation favors induction of Foxp3 in the periphery; however, it remains to be determined how TCR ligand potency influences this process. We characterized the density and affinity of TCR ligand favorable for Foxp3 induction and found that a low dose of a strong agonist resulted in maximal induction of Foxp3 in vivo. Initial Foxp3 induction by weak agonist peptide could be enhanced by disruption of TCR–peptide major histocompatibility complex (pMHC) interactions or alteration of peptide dose. However, time course experiments revealed that Foxp3-positive cells induced by weak agonist stimulation are deleted, along with their Foxp3-negative counterparts, whereas Foxp3-positive cells induced by low doses of the strong agonist persist. Our results suggest that, together, pMHC ligand potency, density, and duration of TCR interactions define a cumulative quantity of TCR stimulation that determines initial peripheral Foxp3 induction. However, in the persistence of induced Foxp3+ T cells, TCR ligand potency and density are noninterchangeable factors that influence the route to peripheral tolerance.
Theoretical Study on Mechanism of Cycloadditional Reaction Between Dichloro-Germylidene and Formaldehyde
Authors: Lu Xiu-hui , Li Yong-qing , Xu Yue-hua , Han Jun-feng , Shi Le-yi
Published: July 2010

Mechanism of the cycloadditional reaction between singlet dichloro-germylidene and formaldehyde has been investigated with MP2/6–31G* method, including geometry optimization, vibrational analysis and energies for the involved stationary points on the potential energy surface. Prom the potential energy profile, we predict that the cycloaddition reaction between singlet dichloro-germylidene and formaldehyde has two competitive dominant reaction pathways, going with the formation of two side products (INT3 and INT4), simultaneously. Both of the two competitive reactions consist of two steps, two reactants firstly form a three-membered ring intermediate INT1 and a twisted four-membered ring intermediate INT2, respectively, both of which are barrier-free exothermic reactions of 41.5 and 72.3 kJ/mol; then INT1 isomerizes to a four-membered ring product P1 via transition state TS1, and INT2 isomerizes to a chlorine-transfer product P2 via transition state TS2, with the barriers of 2.9 and 0.3 kJ/mol, respectively. Simultaneously, P1 and INT2 further react with formaldehyde to form INT3 and INT4, respectively, which are also barrier-free exothermic reaction of 74.9 and 88.1 kJ/mol.
Time-Dependent Stokes Shift from Solvent Dielectric Relaxation
Authors: Xu Jing , Wang Quan-de , Zhu Quan , Fu Ke-xiang , He Fu-cheng , Li Xiang-yuan
Published: July 2010

The Stokes shift response function, which is related to the time dependent solvation energy, is calculated with the dielectric response function and a novel expression of nonequilibrium solvation energy. In the derivation, relationship between the polarization and the dielectric response function is used. With the dipole-in-a-sphere model applied to the system coumarin 343 and water as the solvent, encouraging agreement with the experimental data from Jimenez et al. is obtained [Nature 369, 471 (1994)].
Theoretical Study on Destruction Mechanism of 2,3,7,8-TCDD by O3 and NO3
Authors: Wang Zhi-hua , Wen Zheng-cheng , Xu Jiang-rong , Zhou Jun-hu , Cen Ke-fa
Published: July 2010

In order to improve the destruction efficiency of dioxins and also for developing new dioxin control technology, the destruction mechanisms of 2,3,7,8-tetrachlorodihenzo-p-dioxin (2,3,7,8-TCDD) by O3 and NO3, were investigated employing quantum chemical calculations. For involved reactions, the microcosmic reaction processes were analyzed and depicted in detail based on geometry optimizations made by the B3LYP/6–31G(d) method. At the same time, the reaction activation energies were also calculated at the MP2/6–311G(d,p)//B3LYP/6–31G(d) level. Configuration analysis indicated that 2,3,7,8-TCDD could be destroyed by O3 and NO3 in two different ways. The destruction of 2,3,7,8-TCDD by O3 proceeded via the addition of O3 and the cleavage of C = C while the destruction of 2,3,7,8-TCDD by NO3 proceeded via the substitution of chlorine by NO3. Calculated results show that, the activation energy of the destruction reaction of 2,3,7,8-TCDD by NO3 (267.48 kJ/mol) is much larger than that of the destruction reaction of 2,3,7,8-TCDD by O3 (51.20 kJ/mol). This indicated that the destruction of 2,3,7,8-TCDD by O3 is much more efficient than that of 2,3,7,8-TCDD by NO3. The reason why the activation energy for the destruction reaction of 2,3,7,8-TCDD by NO3 is so large, is also discussed.
Methanol Tolerant Non-noble Metal Co-C-N Catalyst for Oxygen Reduction Reaction Using Urea as Nitrogen Source
Authors: Si Yu-jun , Chen Chang-guo , Yin Wei , Cai Hui
Published: July 2010

A non-noble metal oxygen reduction reaction (ORR) catalyst labeled as Co-C-N(800) was synthesized by heat-treating a mixture of urea, cobalt chloride and acetylene black for 2 h at 800 °C in an inert nitrogen atmosphere. X-ray diffraction pattern indicates that a metallic β-Co is generated after the heat-treating process. The results from cyclic voltammograms show that the obtained Co-C-N(800) catalyst has good ORR catalytic activity in 0.5 mol/L H2SO4 solution. The catalyst is also good at methanol tolerance and stability in the acidic solution.
Microwave Assisted Synthesis of a New Triplet Iridium(III) Pyrazine Complex
Authors: Wu Qiu-hua , Wang Chuan-hong , Song Xi-ming , Zhang Guo-lin
Published: July 2010

A new cyclometalated iridium(III) complex Ir(DPP)3 (DPP = 2,3-diphenylpyrazine) was prepared by reaction of DPP with iridium trichloride hydrate under microwave irradiation. The structure of the complex was confirmed by elemental analysis, 1H NMR, and mass spectroscopy. The UV-Vis absorption and photoluminescent properties of the complex were investigated. The complex shows strong 1MLCT (singlet metal to ligand charge-transfer) and 3MLCT (triplet metal to ligand charge-transfer) absorption at 382 and 504 nm, respectively. The complex also shows strong photoluminescence at 573 nm at room temperature. These results suggest the complex to be a promising phosphorescent material.
On the behaviour of marginal and conditional AIC in linear mixed models
Authors: Greven Sonja , Kneib Thomas
Published: July 2010

In linear mixed models, model selection frequently includes the selection of random effects. Two versions of the Akaike information criterion, aic, have been used, based either on the marginal or on the conditional distribution. We show that the marginal aic is not an asymptotically unbiased estimator of the Akaike information, and favours smaller models without random effects. For the conditional aic, we show that ignoring estimation uncertainty in the random effects covariance matrix, as is common practice, induces a bias that can lead to the selection of any random effect not predicted to be exactly zero. We derive an analytic representation of a corrected version of the conditional aic, which avoids the high computational cost and imprecision of available numerical approximations. An implementation in an R package (R Development Core Team, 2010) is provided. All theoretical results are illustrated in simulation studies, and their impact in practice is investigated in an analysis of childhood malnutrition in Zambia.
Relative Susceptibility of Selected Apple Cultivars to Sooty Blotch and Flyspeck
Authors: Biggs Alan R. , Cooley Daniel R. , Rosenberger David A. , Yoder Keith S.
Published: July 2010

Incidence data for sooty blotch and flyspeck (SBFS), apple diseases caused by a complex of fungi that includes Schizothyrium pomi, Peltaster fructicola, Leptodontidium elatius, and Geastrumia polystigmatis, were collected over several years from planting groups of new apple cultivars and selections planted at multiple locations in either 1995 (23 entries) or 1999 (22 entries) as part of the NE-183 Multistate Project. SBFS incidence on fruit was analyzed, and data from sites in Massachusetts, New York, and Virginia were compared to determine if there were differences among cultivars. Incidence of SBFS varied among cultivars in both the 1995 and 1999 plantings, and among locations in the 1999 plantings. These differences were primarily the result of harvest date, with cultivars that were harvested latest having the highest disease incidences. Lower SBFS incidence on the earlier maturing cultivars apparently resulted from disease avoidance, as these apples were exposed to fewer hours of wetting and high relative humidity, environmental factors favorable for growth of SBFS fungi. Management tactics targeting SBFS are especially critical for cultivars that mature late in the season.

Accepted for publication 13 May 2010. Published 26 July 2010.
Anesthetic Management and Surgical Site Infections in Total Hip or Knee Replacement
Authors: Chang Chuen-Chau , Lin Hsiu-Chen , Lin Hui-Wen , Lin Herng-Ching
Published: July 2010

Background

Epidural or spinal anesthesia involves several mechanisms hypothesized to reduce risk of surgical site infections (SSIs) during this decisive period. This study aims to compare the risk of SSI within 30 days of surgery for patients receiving total hip or knee replacement under general anesthesia versus those under epidural or spinal anesthesia.

Methods

We used the Longitudinal Health Insurance Database of Taiwan. A total of 3,081 patients who underwent primary total hip or knee replacement from 2002 to 2006 were included in the study. Multivariate logistic regression and propensity score analyses were carried out to explore the relationship between method of surgical anesthesia and SSI occurring within 30 days of surgery.

Results

Of the 3,081 sampled patients, 56 patients (1.8%) had 30-day SSIs; 33 (2.8% of all under general anesthesia) of them had general anesthesia, and 23 (1.2% of all under epidural or spinal anesthesia) had epidural or spinal anesthesia (P = 0.002). The odds of SSI for patients receiving total hip or knee replacement under general anesthesia were 2.21 (95% CI = 1.25-3.90, P = 0.007) times higher than those who had the same procedure under epidural or spinal anesthesia, after adjusting for the patient's age, sex, the year of surgery, comorbidities, surgeon's age, and hospital teaching status.

Conclusions

Total hip or knee replacement under general anesthesia is associated with higher risk of SSI compared with epidural or spinal anesthesia. Our results support the evolving concept of long-term consequences of anesthesia and emphasize the anesthesiologist's role in preventing SSIs.
Deposition of Atlantic salmon Salmo salar carcasses in a Scottish upland catchment
Authors: Williams K. L. , Griffiths S. W. , McKelvey S. , Armstrong J. D.
Published: July 2010

Radio telemetry was utilized to track 38 Atlantic salmon Salmo salar across space and time during and following their spawning run on the Conon system, Scotland. The data collected were used to assess the proportion of S. salar able to migrate successfully from an upland oligotrophic area of the catchment and the distribution of the carcasses of those fish that remained. Of these fish, 35% successfully migrated from the study area after the spawning period. The fish that remained were distributed approximately equally between riverine and lacustrine areas, but with a strong tendency to accumulate in regions of relatively slow water flows.
Thermoelectric Determination of Cation Distributions in Fe304‐MgFe204
Authors: TRESTMAN‐MATTS A. , DORRIS S. E. , MASON T. O.
Published: July 2010

Thermoelectric coefficient measurements in the system Fe304‐MgFe204 were used to determine the cation distributions from 600° to 1300°C. The cation distributions obeyed the relationship:

−RT ln KMgCD= 17.4 + 2(−16.4)b (kJ/mol)

where KMgCD is the magnesium distribution constant and b is the tetrahedral Fe3+ concentration. Low‐temperature distributions are consistent with electrical behavior in the system. High‐temperature thermodynamic activities calculated from our distributions agree with experimental values.
Particle Growth during Calcination of Polycation Oxides Synthesized by the Polymeric Precursors Method
Authors: Leite Edson R. , Nobre Marcos A. L. , Cerqueira Marinalva , Longo Elson , Varela Jose Arana
Published: July 2010

The particle‐growth kinetics of sodium niobate and zirconium titanate powders that were processed by the polymeric precursors method were studied. The growth kinetics that were studied for the particle, in the final stage of crystallization, showed that the growth process occurs in two different stages. For temperatures <800°C, the particle‐growth mechanism is associated with surface diffusion, with an activation energy in the range of 40‐80 kJ/mol. For temperatures >800°C, particle growth is controlled by densification of the nanometric particle clusters and by a neck‐size‐controlled particle‐growth mechanism. The results suggest that this behavior was typical of the synthesis method, because two different polycation oxides presented the same behavior.
Optical Spectra of Synthetic Spinels in the System MgAl2O4–MgCr2O4
Authors: Ikeda Ko , Nakamura Yoshinori , Masumoto Kiyoshi , Shima Hiromi
Published: July 2010

Unpolarized optical spectra were measured in the wavelength range 322–1666 nm by the diffuse reflection technique from spinel powders synthesized in the system MgAl2O4–MgCr2O4. The spectra were interpreted by the crystal‐field theory on the basis of trigonally distorted spinel octahedra with D3d symmetry. For chromium‐rich solid solutions, including the MgCr2O4 end‐member, results after peak fittings showed octahedral D3d local symmetry around Cr3+ ions, identical to the crystallographic site symmetry. For chromium‐poor solid solutions, however, octahedral C3v local symmetry was suggested around Cr3+ ions, different from the D3d crystallographically expected.
Thermodynamic Stability of Intergranular Amorphous Films in Bismuth‐Doped Zinc Oxide
Authors: Wang Haifeng , Chiang Yet‐Ming
Published: July 2010

It is shown that the solid‐state equilibrium configuration of Bi‐doped ZnO grain boundaries is a nanometer‐thick amorphous film. Polycrystalline Bi‐doped ZnO was investigated using high‐resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy (STEM). The equilibrium state below the eutectic temperature and at 1 atm total pressure was approached from three different routes: samples were cooled from above the eutectic temperature (Teutectic= 740°C), processed entirely below the eutectic temperature, and desegregated by high applied pressure (1 GPa) followed by annealing at ambient pressure to restore segregation. In all instances, the final state is an amorphous intergranular film 1.0‐1.5 nm in thickness. The results show that a thin intergranular film in this system has lower free energy than the crystal‐crystal grain boundary. The implications of these results for creation of electrically active grain boundaries in zinc oxide varistors are discussed.
Elastic Anisotropy of Plasma‐Sprayed, Free‐standing Ceramics
Authors: Wanner Alexander , Lutz Ekkehard H.
Published: July 2010

This paper reports results on the elastic anisotropy of four different plasma‐sprayed, free‐standing oxide ceramics, obtained by applying an ultrasonic phase spectroscopy technique suitable to measure wave velocities along relatively short pathlengths in extremely porous, strongly attenuating ceramic materials. The as‐sprayed materials are clearly anisotropic, showing a considerably lower stiffness perpendicular to the substrate plane than in directions parallel to that plane. Upon annealing, the materials gradually become more isotropic. It is concluded that the anisotropy is governed by interlamellar, slitlike pores which are formed during the spray‐deposition process and which are aligned preferentially parallel to the substrate surface. Upon annealing, these pores shrink and adopt a more spherical shape, thus reducing the anisotropy.
Elastic and Yield Behavior of Strongly Flocculated Colloids
Authors: Shih Wan Y. , Shih Wei‐Heng , Aksay Ilhan A.
Published: July 2010

We have investigated theorectically the elastic and yield behaviors of strongly flocculated colloids by first examining the yield forces between two particles within the framework of Derjaguin‐Landau‐Verwey‐Overbeck (DLVO) interactions. Under highly attractive conditions, i.e., in the absence of the secondary minimum in the DLVO potential, the radial (tensile) motion between particles is nonelastic because of the lack of an inflection point in the DLVO potential. However, the lateral (shear) motion is shown to be elastic up to a distance ymax, providing a mechanism for the observed elasticity in colloidal gels. If r0 and s0 are, respectively, the closest center‐to‐center and surface‐to‐surface distances between two particles,
image

where zeta is the zeta potential of the particles and alpha a defined constant. Moreover, the yield force between two particles is much smaller in the lateral direction than in the radial direction. These results suggest that yielding of a particulate network is likely to occur through the lateral movements between particles. The yield strain can be approximated as that at which all the bonds in a certain direction have a perpendicular displacement >ymax, resulting in
image

The shear modulus of the network, G′, can be deduced by combining the elastic constant of the lateral movement with the existing elastic theory of a particulate network. The yield stress can be approximated as sigma
image

where A is the Hamaker constant and R the particle radius. These predictions are shown to compare favorably with existing experiments.
Sintering Characteristics in BaTiO3–Nb2O5–Co3O4 Ternary System: I, Electrical Properties and Microstructure
Authors: Chazono Hirokazu , Kishi Hiroshi
Published: July 2010

The influences of the Nb/Co ratio on electrical properties, densification behavior, and microstructural evolution were investigated on ceramics in the ternary system BaTiO3‐Nb2O5‐Co3O4. Temperature‐stable dielectrics were obtained using either a large amount of Nb + Co or a large Nb/Co ratio. The sintering characteristics and electrical properties were studied for the niobium‐rich composition (Nb/Co = 3.00; Comp.N) and the cobalt‐rich composition (Nb/Co = 1.67; Comp.C) with the same Nb + Co amount of 2 at.%. The temperature characteristic of the dielectric constant was flat, irrespective of the firing temperature, for Comp.N, whereas it was dependent largely on the firing temperature for Comp.C. The grains did not grow in Comp.N but grew in Comp.C. The reaction of Nb2O5 and Co3O4 with BaTiO3 yielded secondary phases: Ba6Ti17O40 phase for Comp.N, and a barium‐poor, titanium‐rich, and cobalt‐rich phase for Comp.C. These secondary phases formed a liquid phase during firing. Comp.N contained a larger amount of the secondary phase than Comp.C. It was concluded that the liquid phase contributed little to densification and microstructural evolution in the system BaTiO3‐Nb2O5‐Co3O4.
High‐Temperature Multilayer Composites with Superplastic Interlayers
Authors: Zhang Guo‐Jun , Yue Xue‐Mei , Watanabe Tadahiko
Published: July 2010

A high‐temperature multilayer composite (MLC) with hot hard layers and superplastic layers was proposed in this communication. The hard layer can provide the MLC high‐temperature strength; the superplastic layer can deform plastically at high temperatures, disperse the applied stress, and stop the crack from advancing. Such an MLC was prepared via tape casting in the Al2O3/MoSi2+Mo2B5 system in the present work; in this system, Al2O3 was the hard layer and MoSi2+Mo2B5 was the superplastic layer. The microstructures and the stress‐displacement behaviors of the MLCs were investigated. Finally, the design rules for the high‐temperature MLCs were discussed briefly.
Micromechanical Characterization of Electrophoretic‐Deposited Green Films
Authors: Formento Alessandra , Montanaro Laura , Swain Michael V.
Published: July 2010

Low‐load indentation experiments have been performed on electrophoretic‐deposited films of SiC particles on a graphite substrate. Films with thicknesses between 60 and 300 µm prepared at two current intensities and subsequently dried under different humidities were indented with spherical indenters with nominal radii of 10, 50, and 150 µm. Force‐displacement data were analyzed to determine contact pressure and elastic modulus versus depth results. The modulus and contact pressure behavior with depth exhibited opposite trends with indenter radius: the modulus increase was least for the 10 µm and greatest for the 150 µm, whereas the contact pressure was the inverse. The results may be rationalized by plotting modulus normalized to the ratio “contact radius/film thickness” (a/t), whereas the contact pressure results at small a/t could be normalized when plotted versus contact strain, i.e., contact radius divided by indenter radius (a/R). These approaches enabled the properties of the variously deposited films to be compared. Additional interesting microstructural and cracking behavior patterns are also reported.
Powder Processing, Rheology, and Mechanical Properties of Feedstock for Fused Deposition of Si3N4 Ceramics
Authors: Rangarajan Sriram , Qi Gang , Venkataraman Natesan , Safari Ahmad , Danforth Stephen C.
Published: July 2010

Fused deposition of ceramics (FDC) is a technique in which green parts are fabricated directly from CAD designs. The feedstock for FDC is a 1.778 mm diameter filament that requires a low viscosity and high column strength. This study explores the powder processing science, as well as the rheological and mechanical properties required for a successful FDC feedstock material. GS44 Si3N4 powders were dispersed in RU9 binder using oleyl alcohol (OA). The viscosity of the RU9/OA/Si3N4 mixture was measured as a function of temperature, solids loading, and OA concentration. The mechanical properties of the filament feedstock were evaluated in compression to establish FDC process limits. The feedstock material shows a shear thinning behavior with OA acting mainly as a plasticizer. The viscosity of GS44‐filled RU9 decreases with temperature, and increases with solids content. At 185°C and 55 vol% loading, the viscosity was found to be in the range of 49–7 Pa·s for a corresponding shear rate of 70–1128 s−1. This was sufficiently low for FDC. Based on pressure requirements for FDC extrusion (ΔP), and maximum sustainable stress without buckling by the filament (σE), it has been found that for successful FDC of RU955, 1.1ΔP < σE.
Morphology and Stacking Faults of β‐Silicon Carbide Whisker Synthesized by Carbothermal Reduction
Authors: Seo Won‐Seon , Koumoto Kunihito , Aria Shigeo
Published: July 2010

The main formation reaction for whisker that has been synthesized from SiO2 and carbon black (CB) in a hydrogen‐gas atmosphere was a solid–gas reaction between SiO and CB. The synthesized whiskers were classified into three types, in terms of the morphology, growth direction, and stacking‐fault planes: (i) type A, which has a relatively flat surface and the stacking‐fault planes are perpendicular to the growth direction; (ii) type B, which has a rough surface and the stacking‐fault planes are inclined at an angle of 35° to the growth direction; and (iii) type C, which has a rough sawtooth surface and the stacking faults exist concurrently in three different {111} planes. The observed angles in the deflected and branched whiskers were 125°, 70°, and 109°. These whiskers were composed of mixtures of type A and type B, type A only, or parallel growth by two pairs of type A and type B whiskers. The whisker deflection was closely related to the difference in the growth speed of each type of whisker.
Relative Colloidal Stability in Ethanol of Powders with Si‐O Surface Species
Authors: Fukada Yoko , Nicholson Patrick S.
Published: July 2010

The relative colloidal stability in ethanol of ceramic powders with Si‐O surface groups (Si3N4, SiC, and MoSi2) is reported. SiO2/EtOH suspensions are also examined as a reference. The comparative relationships between pH, particle‐surface charge, zeta potential, stability, and suspension rheology are discussed. The nature and influence of the surface species are determined, and the similarities and differences are compared. DLVO theory was used to define suspension stability, and it was found that non‐oxide particles in EtOH are charge‐stabilized and have viscosity and flow curves that agree with the electrokinetic measurements.