bluuebunny/crossref_metadata_2025 huggingface dataset:
The glass‐forming ability and thermal stability of novolac–phenolic resin
Authors: Guo Kai , Bian Xiufang , Qin Jingyu , Yang Lei
Published: December 2011

Glass‐forming ability and thermal stability of novolac–phenolic resin with different contents of curing agent hexamethylenetramine (HMTA) are investigated. Melt fragility (Mg) and Tgd (Tgd = Tg/Td) are proposed to characterize glass‐forming ability and thermal stability of the novolac–phenolic resin, respectively. It is found that Mg has a negative linear relationship with Tgd. The lower Mg represents the better glass‐forming ability of liquid phenolic resin while the higher Tgd represents the better thermal stability of the fully cured phenolic resin. Further more, Mg establishes a kinetic relationship between glass‐forming ability of liquid uncured and thermal stability of fully cured novolac–phenolic resin in terms of comparing with Tgd. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers
Effects of multiple carbon fillers on the rheology of polycarbonate‐based composites
Authors: Via Michael D. , Morrison Faith A. , King Julia A. , Beach Edsel A. , Wiese Kyle R. , Bogucki Gregg R.
Published: December 2011

Adding conductive carbon fillers to insulating thermoplastic polymers increases the electrical conductivity of the resulting composite, which could allow them to be used in electrostatic dissipative and semiconductive applications. Adding fillers often increases viscosity, which can make the material more difficult to process. In this study, three different carbon fillers [carbon black (CB), carbon nanotubes (CNT), and exfoliated graphite nanoplatelets (GNP)] were studied via three different combinations of two different fillers (CB/CNT, CB/GNP, and CNT/GNP). These filler combinations were studied via three 32factorial designs, which considered the following loading levels: CB: 0, 2, and 5 wt%; CNT: 0, 1, and 5 wt%; and GNP: 0, 2, and 5 wt%. These composites were compounded, injection molded, and tested for electrical conductivity and steady shear viscosity. CB and GNP exhibited classic filler behavior, increasing the composite viscosity with increased filler loading. CNT acted differently, lowering the composite viscosity with increased filler loading. When CB and GNP were combined, the viscosity increase was additive. When CNT was combined with either CB or GNP, the resultant composite had a lower viscosity than the corresponding single filler composite with equivalent loadings of CB or GNP. This viscosity lowering effect of CNT, even at loadings as low as 1 wt%, allows for increased filler loadings of CB or GNP with little impact on processability. Five different formulations (four containing two filler combinations) could be used for electrostatic dissipative applications and seven different formulations (six containing two filler combinations) may be used for semiconductive applications. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers
Towards an Efficient Protocol for the Determination of Triterpenic Acids in Olive Fruit: A Comparative Study of Drying and Extraction Methods
Authors: Goulas Vlasios , Manganaris George A.
Published: December 2011

Introduction

Triterpenic acids, such as maslinic acid and oleanolic acid, are commonly found in olive fruits and have been associated with many health benefits. The drying and extraction methods, as well as the solvents used, are critical factors in the determination of their concentration in plant tissues. Thus, there is an emerging need for standardisation of an efficient extraction protocol that determines triterpenic acid content in olive fruits.

Objective

To evaluate common extraction methods of triterpenic acids from olive fruits and to determine the effect of the drying method on their content in order to propose an optimum protocol for their quantification.

Methodology

The efficacy of different drying and extraction methods was evaluated through the quantification of maslinic acid and oleanolic acid contents using the reversed‐phase HPLC technique.

Results

Data showed that ultrasonic assisted extraction with ethanol or a mixture of ethanol:methanol (1:1, v/v) resulted in the recovery of significantly higher amounts of triterpenic acids than other methods used. The drying method also affected the estimated triterpenic acid content; frozen or lyophilised olive fruit material gave higher yields of triterpenic acids compared with air‐dried material at both 35°C and 105°C.

Conclusion

This study provides a rapid and low‐cost extraction method, i.e. ultrasonic assisted extraction with an eco‐friendly solvent such as ethanol, from frozen or lyophilised olive fruit for the accurate determination of the triterpenic acid content in olive fruit. Copyright © 2011 John Wiley & Sons, Ltd.
Crystallization behavior and nucleation analysis of poly(l‐lactic acid) with a multiamide nucleating agent
Authors: Song Ping , Wei Zhiyong , Liang Jicai , Chen Guangyi , Zhang Wanxi
Published: December 2011

To accelerate the crystallization of poly(L‐lactic acid) (PLLA) and enhance its crystallization ability, a multiamide nucleator (TMC) was introduced into the PLLA matrix. The thermal characteristics, isothermal and nonisothermal crystallization behavior of pure PLLA and TMC‐nucleated PLLA were investigated by differential scanning calorimetry. The determination of thermal characteristics shows that the addition of TMC can significantly decrease the onset temperature of cold crystallization and meanwhile elevate the total crystallinity of PLLA. For the isothermal crystallization process, it is found that the overall crystallization rate is much faster in TMC‐nucleated PLLA than in pure PLLA and increases as the TMC content is increased, however, the crystal growth form and crystalline structure are not influenced much despite the presence of TMC. In the case of nonisothermal crystallization, the nucleation efficiency and nucleation activity were estimated and the results indicate that excellent nucleation‐promoting effect could be achieved when the weight percentage of TMC is chosen between 0.25% and 0.5%. Polarized optical microscopy observation reveals that the nuclei number of PLLA increases and the spherulite size reduces greatly with the addition of TMC. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers
Residual stresses and thermoviscoelastic deformation of laminated film prepared for film insert molding
Authors: Kim Sung Ho , Kim Seong Yun , Lee Seung Hwan , Youn Jae Ryoun
Published: December 2011

Residual stresses and thermoviscoelastic deformation of a laminated film utilized for film insert molding was investigated through measurement of thermal expansion coefficient (CTE) and relaxation modulus. Thermoviscoelastic deformation of the film was also analyzed with numerical analysis by applying measured relaxation modulus, CTE, and residual stress to finite element method (FEM). Stress relaxation of the pristine film showed significantly different behavior from that of the unannealed film during annealing. Effects of the CTE and relaxation modulus on the thermoviscoelastic deformation were predicted by considering thermal shrinkage and structural relaxation. Moreover, numerical results on thermoviscoelastic deformation were in good agreement with experiments when initial stress distribution in the solid specimen was applied to the numerical analysis. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers
Siloxane polymers containing azo moieties synthesized by click chemistry for photo responsive and liquid crystalline applications
Authors: Pandey Someshwarnath , Kolli Balakrishna , Mishra Sarada P. , Samui Asit B.
Published: December 2011

Three new types of siloxane‐based photoactive liquid crystalline polymers containing azo side groups were synthesized through the click chemistry route. The polymers having molecular weight range of 14,000–34,000 g mol−1 were soluble in most of the polar solvents like chloroform, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, and dichloromethane. The photoresponsive trans–cis photoisomerization under UV radiation and cis–trans relaxation process in dark for the polymers were studied. The isomerization rate constants were found to be 0.01–0.04 sec−1 and 1.16*10−4–4.67*10−4 sec−1, respectively. It has been noted that the polymers showed high intensity absorption for n‐π* in chloroform. Both trans and cis forms of azide monomers having azo moiety exhibited molar extinction coefficient (ϵmax) in the range of 22,000–33,000 L mol−1 cm−1. The thermotropic behavior of the polymers was studied by polarizing optical microscope (POM) and differential scanning calorimetry (DSC) experiments. Polymer P1 showed liquid crystalline textures of nematic droplets, whereas P2 showed smectic focal conic texture and nematic droplets. Polymer P1 was also studied for photomechanical bending on exposure to UV radiation. The polymers showed initial degradation temperature in the range of 210–275°C. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Temperature‐based fluorescence measurements of pyrene in block copolymer micelles: Probing micelle core glass transition breadths
Authors: Mok Michelle M. , Lodge Timothy P.
Published: December 2011

Glass transition temperature (Tg) breadths are reported for polystyrene (PS) micelle cores in two series of micelle‐forming block copolymers [PS‐poly(ethylene oxide) and PS‐poly(methyl methacrylate)] with an ionic liquid solvent (1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)amide). An increased level of fluorescent molecules was induced within the cores upon rapid cooling followed by aging. Using fluorescence to monitor dye release with relaxation of this state upon heating, transition onset and end‐point temperatures were defined. The system with the lowest PS‐block molecular weight showed no evidence of a transition above 25 °C; however, in every other case, transitions were observed beginning at ∼40‐45 °C and ending at ∼60‐85 °C. These temperatures closely match PS‐block Tg results measured by differential scanning calorimetry in semidilute solutions of the same materials, suggesting that the transition temperature range correlates strongly to the transition of the cores from fully glassy to fully rubbery. Differences in transition end‐points were related to PS‐block molecular weights and relative copolymer fractions of PS. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
Nanomechanical properties in ultrathin polymer films: Measurement on rectangular versus circular bubbles
Authors: Xu Shanhong , O'Connell Paul A. , McKenna Gregory B. , Castagnet Sylvie
Published: December 2011

Prior studies of inflation of circular membranes of ultrathin polystyrene (PS) films have evidenced a reduced glass transition temperature (Tg) and rubbery stiffening, whose origins remain unclear. Here, we describe results from inflation of rectangular, ultrathin films of the same PS material. The bubble shapes obtained from the experiment are consistent with finite element (FE) simulations. The accuracy of three approximate solutions for modulus obtained from the inflation of the thin, rectangular films was evaluated by comparison with FE analysis. The best among the three solutions was used to determine the creep compliance and rubbery stiffness of the thin films. It is found that the reduction of Tg and the rubbery stiffening for rectangular bubbles are consistent with results obtained using circular bubbles, although there is some indication that the rectangular bubbles give somewhat greater rubbery stiffening. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
Computational study of the patterns of weaker intramolecular hydrogen bonds stabilizing acylphloroglucinols
Authors: Mammino Liliana , Kabanda Mwadham M.
Published: December 2011

Acylphloroglucinols (ACPLs) are polyphenolic compounds derivative from phloroglucinol, characterized by the presence of at least one COR group and exhibiting a variety of biological activities, which makes them interesting for drug development possibilities. This study investigates patterns in the ways in which weaker intramolecular hydrogen bonds contribute to their conformational stabilization, considering the CH···O H‐bonds, present in all ACPLs, and the OH···π H‐bonds, present in ACPLs in which one or more substituents contain a π bond or system sufficiently close to a phenol OH for the H‐bond to be possible. The results in vacuo and in three different solvents (chloroform, acetonitrile, and water) show that, whereas CH···O plays a significant roles in all these media, the role of OH···π decreases with increasing solvent polarity. Calculations in vacuo are performed at various levels to enable performance comparisons; calculations in solution use the polarizable continuum model. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Theoretical study of the chemical reactivity and molecular quantum similarity in a series of derivatives of 2‐adamantyl‐thiazolidine‐4‐one using density functional theory and the topo‐geometrical superposition approach
Authors: Morales‐Bayuelo Alejandro , Baldiris Rosa , Torres Juan , Torres Juan E. , Vivas‐Reyes Ricardo
Published: December 2011

A theoretical study for the determination of chemical reactivity of a series of 2‐adamantyl‐thiazolidine‐4‐one derivatives was performed. These molecules are inhibitors of inverse transcriptase activity of human immunodeficiency virus type 1 (HIV‐1) that prevents the replication of HIV‐1 in cells without causing an appreciable effect on other retroviral particles or cellular polymerases. To determine the nature of the bond, enzyme substrate was used for quantum similarity molecular calculations, using the alignment of topo‐geometrical superposition approach, solving the problem of finding the best alignment. The reactivity descriptors provide an appropriate methodology to evaluate molecular quantum similarity of these molecular structures, in the context of the density functional theory, taking into account the electronic effects quantified by the quantum similarity descriptor of Coulomb, which turned out to be the best molecular descriptor to describe the electron correlation structures; the determination of the reactive sites is of great importance for the determination of chemical reactivity, providing a bridge between the fields of chemical reactivity, and molecular quantum similarity allows us to find new characteristics and properties of reactivity on these kinds of molecules. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Measurement uncertainty in single, double and triple isotope dilution mass spectrometry
Authors: Vogl Jochen
Published: December 2011

Triple IDMS has been applied for the first time to the quantification of element concentrations. It has been compared with single and double IDMS obtained on the same sample set in order to evaluate the advantages and disadvantages of triple IDMS over single and double IDMS as an analytical reference procedure. The measurement results of single, double and triple IDMS are indistinguishable, considering rounding due to the individual measurement uncertainties. As expected, the relative expanded uncertainties (k = 2) achieved with double IDMS (0.08 %) are dramatically smaller than those obtained with single IDMS (1.4 %). Triple IDMS yields the smallest relative expanded uncertainties (k = 2, 0.077 %) unfortunately at the expense of a much higher workload. Nevertheless triple IDMS has the huge advantage that the isotope ratio of the spike does not need to be determined. Elements with high memory effects, highly enriched spikes or highest metrological requirements may be typical applications for triple IDMS. Copyright © 2011 John Wiley & Sons, Ltd.
Fungating Thyroid Cancer: A Complex Clinical Scenario
Authors: Nabawi A. S. , Al Wagih H. F. , Hemeida M. A. , Koraitim T. Y. , Moussa M. , Ezzat Tarek
Published: December 2011

Background

Most research reporting the management of advanced thyroid cancer focuses on major aerodigestive system or vessel involvement. In the present study, we investigated patients with locally advanced thyroid cancers who presented with malignant skin infiltration. The term fungating thyroid cancer (fTC) has been used to describe such a condition.

Methods

The study was based on prospective collection of clinical, laboratory, imaging, and pathological data of all patients admitted to the head and neck and endocrine surgery unit, Main University Hospital, Alexandria School of Medicine, during the period April 2005–March 2011.

Results

Eleven patients were referred with fTC, eight of whom had undergone subtotal thyroidectomy for an undiagnosed well‐differentiated thyroid cancer (DTC) in another institution. The final pathological diagnosis showed (DTC, n = 3), poorly differentiated thyroid cancer (n = 5), anaplastic cancer (n = 2), and medullary thyroid cancer (n = 1). Extensive resections and reconstruction using flaps (pectoralis major, n = 6; deltopectoral, n = 1; sternocleidomastoid, n = 1) were undertaken. Complete tumor clearance (R0) was achieved in one patient and the others had microscopic (R1, n = 6) or macroscopic (R2, n = 1) residual disease. The three patients who did not undergo operation died within one month of presentation. The latest review of the eight patients who did undergo operation ranged from 3 to 6 months, but their survival remains unknown as access for follow‐up was limited.
Howard Conference on Jobs: A Union Perspective
Authors: Golash Michael
Published: December 2011

The article looks critically at the many job creation proposals formulated by scholars and at federal legislation mandating full employment. It concludes that the lack of jobs in a modern capitalist society is rational and to end unemployment requires a systemic change.
Double‐stranded RNA induces S100 gene expression by a cycloheximide‐sensitive factor
Authors: Voss Andreas , Gescher Kirsten , Hensel Andreas , Nacken Wolfgang , Zänker Kurt S. , Kerkhoff Claus
Published: December 2011

Viral double‐stranded RNA (dsRNA) and its synthetic analog polyI:C are recognized via multiple pathways and induce the expression of genes related to inflammation. In the present study, we demonstrated the polyI:C‐induced gene expression of the damage associated molecular pattern (DAMP) molecules S100A8 and S100A9, while other S100 genes were not affected. Cycloheximide and Brefeldin A treatment revealed both the expression of S100A8 and S100A9 as secondary response genes and the involvement of polyI:C‐induced cytokines herein. Several type I and type III interferons such as IFNβ, IL‐20, IL‐24, and IFNλ/IL‐29 were expressed in response to polyI:C, however, they failed to induce S100A8 and S100A9 gene expression. These data indicate the involvement of the danger molecule S100A8/A9 in the resistance against viruses.
Religious‐based portfolio selection
Authors: Lu Jin‐Ray , Chan Chih‐Ming
Published: December 2011

We examine religious attendance and portfolio selection decisions for an individual with religious beliefs within a continuous‐time framework. Our findings are three‐fold. First, religious contributions increase with wealth capital, the degree of religious devotion, and an increase in the wage level. Second, religious attendance positively relates to wealth capital and the performance of stock investments, but negatively correlates with wage return rates. Third, participation in religious activities can result in declining demand for risky asset investments. Theoretically, this study explains how individuals’ portfolio choices correlate with their religious activities.
Eclogites from the Belomorian Mobile Belt (Kola Peninsula): geology and petrology
Authors: Shchipansky A.A. , Khodorevskaya L.I. , Konilov A.N. , Slabunov A.I.
Published: December 2011

The paper focuses on the metamorphic geology of the oldest crustal eclogites discovered in the Late Archean tonalite-trondhjemite-granodiorite (TTG) complex of the Belomorian Mobile Belt on the Kola Peninsula. Eclogite bodies are, most likely, widespread. We studied one of the key objects, the Kuru-Vaara quarry, where several tens of retrogressed eclogite blocks randomly embedded in the TTG gneisses were stripped at the benches. Based on the field observations, two visually different types of eclogites have been recognized: “southern”, strongly retrogressed coarse-grained, and “northern”, well-preserved fine-grained. The southern eclogite blocks bear evidence of their partial melting with the formation of veins and melt percolation channels. The northern eclogite blocks show no evidence of melting. Despite the significant mineralogic difference, both types of eclogites can be assigned to amphibole eclogite facies. The applied jadeite solubility geobarometers yielded the minimum pressures of ∼12 kbar for the northern eclogites and ∼14–14.5 kbar for the southern ones. The used geothermometers yielded ∼700°C and ∼750°C, respectively. But the presence of quartz lamellae in Na-clinopyroxenes in both types of eclogites and their bulk compositions corresponding to high-Mg basalts suggest that the Kuru-Vaara eclogites might have reached the field of ultrahigh-pressure metamorphism. Analysis of the tentative P-T paths of metamorphic evolution for both types of eclogites showed that their burial–exhumation cycle might have taken as short as a few million years. The set of presented data suggests that the formation of the Kuru-Vaara eclogites was related to the subduction of the Archean oceanic crust, which should have differed in composition and structure from the modern oceanic crust.
Modeling of deep-seated high-alumina parageneses on the basis of the stability fields of corundum- and spinel-normative assemblages of the system CaO–MgO–Al2O3–SiO2
Authors: Surkov N.V. , Gartvich Yu.G.
Published: December 2011

To elaborate physicochemical models for the origin of crystalline rocks, experimental studies of the field of high-alumina assemblages of the system CaO–MgO–Al2O3–SiO2 were carried out at 10–30 kbar and 1250–1535 °C. We have determined the phase relations between the melt (L) and An, Sp, Cpx, Cor, and Ga, the slope of the rays of the monovariant reactions An + Sp = Cpx + Cor + (Ga) and L = Cpx +Ga + Cor + Sp, the position of the nonvariant point (An, Sp, Cpx, Cor, Ga, L), and the compositions of phases participating in these reactions. Based on a topological analysis of the studied segment of the system CaO–MgO–Al2O3–SiO2, we have substantiated that “eclogitization” must follow the reaction Opx + An + Sp = Cpx + Ga. A fundamental continuous series of eutectic monovariant equilibria was observed: L = Cpx + Opx + Fo + An, L = Cpx + Opx + An + Sp, L = Cpx (+ Ga) + An + Sp, and L = Cpx + Cor (+ Ga) + An. A change in the melt composition in this series of eutectic reactions depending on pressure must reflect the most likely magma genesis trend in nature. Comparision of the composition fields in which the above series of reactions is observed with the composition fields of the rocks of magmatic formations showed that this series is most similar to the alkali-earth series of rocks. The mineralogical compositions of cumulates and phenocrysts found in the effusive and dike varieties of these rocks correspond to unique sets of subsolidus phase associations and individual subsolidus phases crystallizing in this fundamental eutectic series.
Nano-structuring of solid surface by extreme ultraviolet Ar8+ laser
Authors: Kolacek K. , Straus J. , Schmidt J. , Frolov O. , Prukner V. , Shukurov A. , Holy V. , Sobota J. , Fort T.
Published: December 2011

This work demonstrates the patterning of polymethylmethacrylate (PMMA) by ablation with Ar8+ ion laser (λ = 46.9 nm) pumped by pulse, high-current, capillary-discharge. For focusing a long-focal spherical mirror (R = 2100 mm) covered by 14 double-layer Sc-Si coating was used. The ablated focal spots demonstrate not only that the energy of our laser is sufficient for such experiments, but also that the design of focusing optics must be more sophisticated: severe aberrations were revealed — an irregular spot shape and strong astigmatism with astigmatic difference as large as 16 mm. In some cases, on the bottom of ablated spots a laser-induced periodic surface structure appeared. Finally, an illumination of the sample through quadratic hole 7.5 × 7.5 µm, standing in contact with PMMA substrate ablated from the surface a strongly developed two-dimensional diffraction pattern (period in the center about 125 nm).
Guzmán Mound: A Late Preclassic Salt works on south coast of Guatemala
Authors: Nance C. Roger
Published: December 2011

Salvage excavation of a small mound on the south coast of Guatemala revealed evidence of Late Preclassic salt production. Most potsherds are of a crude, thin-walled utility ware believed to have been used in evaporating salt water over fires. Level-by-level attribute analysis suggests evolution of a more efficient vessel form for this purpose. A typological study of fine ware and radiocarbon dating firmly position the mound chronologically. Charcoal was abundant; daub and elongated hearths probably figured in the technology. Also, the absence of edible plant remains and the scarcity of obsidian blades and animal bone add to the picture of a specialized, salt-producing locality. The represented salt-making technology is partially reconstructed using comparative ethnographic, ethnohistorical, and archaeological sources from southern Mesoamerica.
The Children of Copan:Issues in paleopathology and paleodemography
Authors: Storey Rebecca
Published: December 2011

The estimated 600 individuals in the Copan skeletal sample make it one of the largest and most important collections from Precolumbian Mesoamerica. The sample is analyzed using a bioarchaeological approach. An overview of the goals of the osteological study and its progress are presented. As an illustration of the results obtainable from osteological analysis, mortality patterns and the incidence of enamel defects in the deciduous dentition of the children of an elite compound, 9N-8, are discussed. Even at an early stage of analysis, children commonly have evidence of health stress that is relevant to understanding the collapse of the Classic Maya society at Copan.
THE BURDEN OF UNANTICIPATED INFLATION: ANALYSIS OF AN OVERLAPPING-GENERATIONS MODEL WITH PROGRESSIVE INCOME TAXATION AND STAGGERED PRICES
Authors: Heer Burkhard , Maußner Alfred
Published: December 2011

Inflation is often associated with a loss for the poor in the medium and long term. We study the short-run redistributive effects of unanticipated inflation in a dynamic optimizing sticky price model of the business cycle. Agents are heterogeneous with regard to their age and their productivity. We emphasize three channels of the effect of inflation on income distribution: (1) factor prices, (2) “bracket creep,” and (3) sticky pensions. Unanticipated inflation that is caused by monetary expansion is found to reduce income inequality. In particular, an increase of the money growth rate by one standard deviation results in a 1% drop of the Gini coefficient of disposable income if extra tax revenues are transferred lump-sum to the households.
XSB: Extending Prolog with Tabled Logic Programming
Authors: SWIFT TERRANCE , WARREN DAVID S.
Published: December 2011

The paradigm of Tabled Logic Programming (TLP) is now supported by a number of Prolog systems, including XSB, YAP Prolog, B-Prolog, Mercury, ALS, and Ciao. The reasons for this are partly theoretical: tabling ensures termination and optimal known complexity for queries to a large class of programs. However, the overriding reasons are practical. TLP allows sophisticated programs to be written concisely and efficiently, especially when mechanisms such as tabled negation and call and answer subsumption are supported. As a result, TLP has now been used in a variety of applications from program analysis to querying over the semantic web. This paper provides a survey of TLP and its applications as implemented in the XSB Prolog, along with discussion of how XSB supports tabling with dynamically changing code, and in a multi-threaded environment.
The present‐day decadal solar cycle modulation of Earth's radiative forcing via charged H2SO4/H2O aerosol nucleation
Authors: Kazil J. , Zhang K. , Stier P. , Feichter J. , Lohmann U. , O'Brien K.
Published: December 2011

The decadal solar cycle modulation of Earth's radiative forcing via ionization of the atmosphere by galactic cosmic rays, aerosol formation from the gas phase, and the response of clouds to aerosol is quantified for the first time with a climate model that represents and couples the relevant processes. Simulations are conducted for solar maximum and minimum conditions, with present‐day anthropogenic aerosol and aerosol precursor gas emissions, and contemporary large‐scale meteorology. The solar cycle signal appears in atmospheric ionization, aerosol formation from the gas phase, aerosol concentrations, aerosol optical depth, and in cloud properties, and is most pronounced at mid‐ and high latitudes. The resulting solar cycle modulation of Earth's radiative forcing exhibits a distinct hemispheric asymmetry, with peak values of −0.14 W m−2 in the southern and −0.06 W m−2in the northern mid‐latitudes. Globally and annually averaged, the solar cycle modulation of Earth's radiative forcing, arising from the increase in atmospheric ionization by galactic cosmic rays from solar maximum to minimum, via charged nucleation of aerosol, the direct aerosol effect, and the cloud albedo effect, amounts to −0.05 W m−2. A limited relevance of this variation for the Earth's atmosphere and climate can be inferred, given that Earth's radiative forcing changes by −0.24 W m−2 from solar maximum to minimum because of a decrease in total solar irradiance.
First‐principles study of high‐pressure elasticity of CF‐ and CT‐structure MgAl2O4
Authors: Yin Kun , Zhou Huiqun , Huang Qian , Sun Yicheng , Xu Shijin , Lu Xiancai
Published: December 2011

The high‐pressure elastic properties of aluminous phases in the basaltic crust of subducted slabs are of interest since they may play important role in the cause of lower mantle seismic anomalies especially at the mid‐mantle depth. The athermal elasticity of the Ca‐Ferrite (CF) and Ca‐Titanate (CT) structure MgAl2O4which are believed to be constituents of the aluminous bearing phases in subducted basalt was performed by first‐principles calculations in the framework of density functional theory. The full elastic constant tensors of the two orthorhombic phases were reported at pressures up to 80 GPa. It has been reported by experiment that a phase transition of CF to CT occurred around 40 GPa corresponding to a depth of about 1000 km. At the transition pressure, (1) the polycrystalline isotropic compressional (P) and shear (S) wave velocities of CT are about 0.7% and 1.6% faster than CF, respectively; (2) both phases show great elastic anisotropy and the fastest travelling direction of P‐wave is along the shortest axis which is parallel to the triangle channels (i.e., [001] for CF and [100] for CT); (3) the largest velocity variation of two orthogonal S‐waves at [001] of CT becomes 25% which is three times larger than that at the corresponding [100] direction of CF. The large velocity variation in S‐waves implies the shear wave splitting observed in the mid‐mantle depth of subducted zones is possible related to the elastic anisotropy of aluminous phases in subducted slabs.
A physical model for seismic noise generation from sediment transport in rivers
Authors: Tsai Victor C. , Minchew Brent , Lamb Michael P. , Ampuero Jean‐Paul
Published: December 2011

Measuring sediment flux in rivers remains a significant problem in studies of landscape evolution. Recent studies suggest that observations of seismic noise near rivers can help provide such measurements, but the lack of models linking observed seismic quantities to sediment flux has prevented the method from being used. Here, we develop a forward model to describe the seismic noise induced by the transport of sediment in rivers. The model provides an expression for the power spectral density (PSD) of the Rayleigh waves generated by impulsive impacts from saltating particles which scales linearly with the number of particles of a given size and the square of the linear momentum. After incorporating expressions for the impact velocity and rate of impacts for fluvially transported sediment, we observe that the seismic noise PSD is strongly dependent on the sediment size, such that good constraints on grain size distribution are needed for reliable estimates of sediment flux based on seismic noise observations. The model predictions for the PSD are consistent with recent measurements and, based on these data, a first attempt at inverting seismic noise for the sediment flux is provided.
Controls on the autochthonous production and respiration of organic matter in cryoconite holes on high Arctic glaciers
Authors: Telling Jon , Anesio Alexandre M. , Tranter Martyn , Stibal Marek , Hawkings Jon , Irvine‐Fynn Tristram , Hodson Andy , Butler Catriona , Yallop Marian , Wadham Jemma
Published: December 2011

There is current debate about whether the balance of photosynthesis and respiration has any impact on the net accumulation of organic matter on glacier surfaces. This study assesses controls on rates of net ecosystem production (NEP), respiration, and photosynthesis in cryoconite holes during the main melt season (June–August 2009) on three valley glaciers in Svalbard. Cryoconite thickness and organic matter content explained 87% of the total variation in rates of respiration (in units of volume), and organic matter (but not sediment depth) was a significant (p< 0.05) control on photosynthesis (by volume). The average rates of respiration and gross photosynthesis within the cryoconite holes were overall closely balanced, ranging from net autotrophic to heterotrophic. Sediment depth explained over half the variation of NEP, with net autotrophic rates typical only in sediment <3 mm thick. The measured rates of NEP were not sufficient to account for the organic matter which has likely accumulated in the cryoconite on timescales of less than decades, suggesting three alternatives for the source of the organic matter. First, the glacier surface may have received windblown allochthonous organic material from surrounding environments. Second, cryoconite may consist of in‐washed autochthonous material from the glacier surface which has comparable organic carbon content. Third, much of the organic matter may have accumulated in the hole during a nascent period, when rates of NEP were much higher. The cycling of autochthonous labile carbon produced by phototrophs may sustain a significant proportion of the total in situ microbial activity within cryoconite holes.
The Effect of Intertalker Variations on Acoustic–Perceptual Mapping in Cantonese and Mandarin Tone Systems
Authors: Peng Gang , Zhang Caicai , Zheng Hong-Ying , Minett James W. , Wang William S.-Y.
Published: December 2011

Purpose

This study investigates the impact of intertalker variations on the process of mapping acoustic variations on tone categories in two different tone languages.

Method

Pitch stimuli manipulated from four voice ranges were presented in isolation through a blocked-talker design. Listeners were instructed to identify the stimuli that they heard as lexical tones in their native language.

Results

Tone identification of Mandarin listeners exhibited relatively stable normalization regardless of the voice, whereas tone identification of Cantonese listeners was unstable and susceptible to the influence of intertalker variations. In the case of Cantonese listeners, intertalker variations had a larger effect on the perception of F0 height dimension than of F0 slope dimension.

Conclusion

The comparison between Cantonese and Mandarin listeners' performances reveals an interaction of intertalker variations and the types of tone contrasts in each language. For Cantonese tones, which depend heavily on F0 height distinctions, intertalker variations result in F0 overlapping and, consequently, ambiguities among them in isolated tone perception. For Mandarin tones, which are distinctive in terms of their F0 contours, the differences in F0 contours alone seem sufficient to elicit reliable tone identification. Intertalker variations therefore have relatively limited effect on Mandarin tone perception.
Coherence depression in stochastic excitable systems with two-frequency forcing
Authors: Yu Na , Longtin André
Published: December 2011

We study the response of two generic neuron models, the leaky integrate-and-fire (LIF) model and the leaky integrate-and-fire model with dynamic threshold (LIFDT) (i.e., with memory) to a stimulus consisting of two sinusoidal drives with incommensurate frequency, an amplitude modulation (“envelope”) noise and a relatively weak additive noise. Spectral and coherence analysis of responses to such naturalistic stimuli reveals how the LIFDT model exhibits better correlation between modulation and spike train even in the presence of both noises. However, a resonance-induced synchrony, occurring when the beat frequency between the sinusoids is close to the intrinsic neuronal firing rate, decreases the coherence in the dynamic threshold case. Under suprathreshold conditions, the modulation noise simultaneously decreases the linear spectral coherence between the spikes and the whole stimulus, as well as between spikes and the stimulus envelope. Our study shows that the coefficient of variation of the envelope fluctuations is positively correlated with the degree of coherence depression. As the coherence function quantifies the linear information transmission, our findings indicate that under certain conditions, a transmission loss results when an excitable system with adaptive properties encodes a beat with frequency in the vicinity of its mean firing rate.
Logical stochastic resonance with correlated internal and external noises in a synthetic biological logic block
Authors: Dari Anna , Kia Behnam , Bulsara Adi R. , Ditto William L.
Published: December 2011

Following the advent of synthetic biology, several gene networks have been engineered to emulate digital devices, with the ability to program cells for different applications. In this work, we adapt the concept of logical stochastic resonance to a synthetic gene network derived from a bacteriophage λ. The intriguing results of this study show that it is possible to build a biological logic block that can emulate or switch from the AND to the OR gate functionalities through externally tuning the system parameters. Moreover, this behavior and the robustness of the logic gate are underpinned by the presence of an optimal amount of random fluctuations. We extend our earlier work in this field, by taking into account the effects of correlated external (additive) and internal (multiplicative or state-dependent) noise. Results obtained through analytical calculations as well as numerical simulations are presented.
Brownian motors and stochastic resonance
Authors: Mateos José L. , Alatriste Fernando R.
Published: December 2011

We study the transport properties for a walker on a ratchet potential. The walker consists of two particles coupled by a bistable potential that allow the interchange of the order of the particles while moving through a one-dimensional asymmetric periodic ratchet potential. We consider the stochastic dynamics of the walker on a ratchet with an external periodic forcing, in the overdamped case. The coupling of the two particles corresponds to a single effective particle, describing the internal degree of freedom, in a bistable potential. This double-well potential is subjected to both a periodic forcing and noise and therefore is able to provide a realization of the phenomenon of stochastic resonance. The main result is that there is an optimal amount of noise where the amplitude of the periodic response of the system is maximum, a signal of stochastic resonance, and that precisely for this optimal noise, the average velocity of the walker is maximal, implying a strong link between stochastic resonance and the ratchet effect.
Surface area of the domain visited by a spherical Brownian particle
Authors: Berezhkovskii Alexander M. , Bezrukov Sergey M.
Published: December 2011

A spatial domain swept out by a spherical particle, whose center follows a Wiener trajectory, is referred to as a Wiener sausage. The present study focuses on the surface area of the Wiener sausage. Using intuitive arguments we derive the mean and variance of the surface area, as well as the asymptotic behavior of its probability density in the limits when the area tends to zero and infinity.
Nonlinear dynamics of skin potentials in the electrosensory paddlefish
Authors: Hofmann Michael H. , Wilkens Lon A.
Published: December 2011

It is known that steady skin potentials are present in fishes due to chloride pumps in the gills and in the skin. We have found previously that these skin potentials can fluctuate and oscillate in the electrosensory paddlefish. Here we show that larger, discharge like potentials can be triggered by applying external electric fields in the water surrounding the fish. These resemble action potentials in nerve cells, but have a longer time scale. Like action potentials, these discharges travel laterally in the skin. They start at the tip of the rostrum and propagate caudally to the tip of the gill covers. They follow the all-or-nothing rule and need some refractory period before they can be evoked again. This is the first time that such discharges, so strikingly similar to action potentials, have been described at the level of a whole organism.
Planar waveguide with “twisted” boundary conditions: Discrete spectrum
Authors: Borisov Denis , Cardone Giuseppe
Published: December 2011

We consider a planar waveguide with combined Dirichlet and Neumann conditions imposed in a “twisted” way. We study the discrete spectrum and describe it dependence on the configuration of the boundary conditions. In particular, we show that in certain cases the model can have discrete eigenvalues emerging from the threshold of the essential spectrum. We give a criterium for their existence and construct them as convergent holomorphic series.
Adiabatic effects on nonlinear dust-acoustic solitary and shock waves in a strongly coupled dusty plasma
Authors: Rahman M. S. , Mamun A. A.
Published: December 2011

A theoretical investigation has been performed on a strongly coupled dusty plasma containing strongly correlated negatively charged dust grains and weakly correlated adiabatic electrons and ions. The adiabatic effects on the dust-acoustic (DA) solitary and shock waves propagating in such a strongly coupled dusty plasma are taken into account. The DA solitary and shock waves are found to exist with negative potential only. It has been shown that the strong correlation among the charged dust grains is a source of dissipation and is responsible for the formation of the DA shock waves. It has also been found that the effects of adiabaticity significantly modify the basic features (e.g., amplitude, width, speed, etc.) of the DA solitary and shock waves. It has been suggested that a laboratory experiment be performed to test the theory presented in this work.
Low-loss flake-graphene saturable absorber mirror for laser mode-locking at sub-200-fs pulse duration
Authors: Cunning B. V. , Brown C. L. , Kielpinski D.
Published: December 2011

Saturable absorbers are a key component for mode-locking femtosecond lasers. Polymer films containing graphene flakes have recently been used in transmission as laser mode-lockers but suffer from high nonsaturable loss, limiting their application in low-gain lasers. Here, we present a saturable absorber mirror based on a film of pure graphene flakes. The device is used to mode lock an erbium-doped fiber laser, generating pulses with state-of-the-art, sub-200-fs duration. The laser characteristic indicates that the film exhibits low nonsaturable loss (13% per pass) and large absorption modulation depth (45% of low-power absorption).
Determination of energy scales in few-electron double quantum dots
Authors: Taubert D. , Schuh D. , Wegscheider W. , Ludwig S.
Published: December 2011

The capacitive couplings between gate-defined quantum dots and their gates vary considerably as a function of applied gate voltages. The conversion between gate voltages and the relevant energy scales is usually performed in a regime of rather symmetric dot-lead tunnel couplings strong enough to allow direct transport measurements. Unfortunately, this standard procedure fails for weak and possibly asymmetric tunnel couplings, often the case in realistic devices. We have developed methods to determine the gate voltage to energy conversion accurately in the different regimes of dot-lead tunnel couplings and demonstrate strong variations of the conversion factors. Our concepts can easily be extended to triple quantum dots or even larger arrays.
Formation of metallic colloids in CaF2 by intense ultraviolet light
Authors: Rix Stephan , Natura Ute , Loske Felix , Letz Martin , Felser Claudia , Reichling Michael
Published: December 2011

Highest purity CaF2 single crystals are irreversibly modified when irradiated with millions of pulses of 193 nm light at fluences of 120 mJ/cm2. Mie theory explains the observed haze by attributing the wavelength dependent extinction and the ratio between absorption and scattering to metallic colloids with radii in the range of 20 to 30 nm and a fractional volume of up to 2.8·10-7. Non-contact scanning force microscopy (NC-AFM) measurements performed on a surface produced by in-vacuo cleavage reveals that laser irradiation additionally produces a 104 times higher volume density of colloids with a radius of 1 to 2 nm.
Book Reviews
Authors: ALEXANDER Huw
Published: December 2011

Access‐Right: The Future of Digital Copyright Law Zohar Efroni New York, Oxford University Press, 2010, 632pp. 978‐0199734078, $95 hbk Whenever a copyright law is to be made or altered, then the idiots assemble. (Mark Twain's Notebook, 1902–1903)
Polarity sets the stage for cytokinesis
Authors: Hehnly Heidi , Doxsey Stephen
Published: December 2011

Cell polarity is important for a number of processes, from chemotaxis to embryogenesis. Recent studies suggest a new role for polarity in the orchestration of events during the final cell separation step of cell division called abscission. Abscission shares several features with cell polarization, including rearrangement of phosphatidylinositols, reorganization of microtubules, and trafficking of exocyst-associated membranes. Here we focus on how the canonical pathways for cell polarization and cell migration may play a role in spatiotemporal membrane trafficking events required for the final stages of cytokinesis.
Increased Leaf Angle1, a Raf-Like MAPKKK That Interacts with a Nuclear Protein Family, Regulates Mechanical Tissue Formation in the Lamina Joint of Rice
Authors: Ning Jing , Zhang Baocai , Wang Nili , Zhou Yihua , Xiong Lizhong
Published: December 2011

Mitogen-activated protein kinase kinase kinases (MAPKKKs), which function at the top level of mitogen-activated protein kinase cascades, are clustered into three groups. However, no Group C Raf-like MAPKKKs have yet been functionally identified. We report here the characterization of a rice (Oryza sativa) mutant, increased leaf angle1 (ila1), resulting from a T-DNA insertion in a Group C MAPKKK gene. The increased leaf angle in ila1 is caused by abnormal vascular bundle formation and cell wall composition in the leaf lamina joint, as distinct from the mechanism observed in brassinosteroid-related mutants. Phosphorylation assays revealed that ILA1 is a functional kinase with Ser/Thr kinase activity. ILA1 is predominantly resident in the nucleus and expressed in the vascular bundles of leaf lamina joints. Yeast two-hybrid screening identified six closely related ILA1 interacting proteins (IIPs) of unknown function. Using representative IIPs, the interaction of ILA1 and IIPs was confirmed in vivo. IIPs were localized in the nucleus and showed transactivation activity. Furthermore, ILA1 could phosphorylate IIP4, indicating that IIPs may be the downstream substrates of ILA1. Microarray analyses of leaf lamina joints provided additional evidence for alterations in mechanical strength in ila1. ILA1 is thus a key factor regulating mechanical tissue formation at the leaf lamina joint.