bluuebunny/crossref_metadata_2025 huggingface dataset:
Server‐aided batch verification signature schemes in the multiple‐signer setting
Authors: Wang Bin , Zhao Qing
Published: April 2013

Server‐aided verification (SAV) signature schemes are useful for power‐constrained devices since a powerful server can assist in performing costly operations such as pairing operations. Wu et al. defined security notions for SAV signature schemes and constructed SAV protocols for some existing signature schemes. We extend their work by introducing a new notion called server‐aided batch verification (SABV) signature schemes, which allows signatures on (possibly) different messages by (possibly) different signers to be simultaneously verified with the help of an honest server. Then, we define completeness, soundness, and existential unforgeability for SABV signature schemes in the multiple‐signer setting. In the following, we design SABV protocols for Waters signature and Boneh–Lynn–Shacham signature, respectively, and prove that these protocols meet the requirement of soundness defined in this paper. Finally, we evaluate the performance of the proposed SABV protocols to show that the cost of a verifier can be further reduced compared with the corresponding SAV protocols presented by Wu et al. Copyright © 2013 John Wiley & Sons, Ltd.
Dual Growth Factor Delivery Using Biocompatible Core–Shell Microcapsules for Angiogenesis
Authors: Choi Dong Hoon , Subbiah Ramesh , Kim Ik Hwan , Han Dong Keun , Park Kwideok
Published: April 2013

An optimized electrodropping system produces homogeneous core–shell microcapsules (C‐S MCs) by using poly(L‐lactic‐co‐glycolic acid) (PLGA) and alginate. Fluorescence imaging clearly shows the C‐S domain in the MC. For release control, the use of high‐molecular‐weight PLGA (HMW 270 000) restrains the initial burst release of protein compared to that of low‐MW PLGA (LMW 40 000). Layer‐by‐layer (LBL) assembly of chitosan and alginate on MCs is also useful in controlling the release profile of biomolecules. LBL (7‐layer) treatment is effective in suppressing the initial burst release of protein compared to no LBL (0‐layer). The difference of cumulative albumin release between HMW (7‐layer LBL) and LMW (0‐layer LBL) PLGA is determined to be more than 40% on day 5. When dual angiogenic growth factors (GFs), such as platelet‐derived GF (PDGF) and vascular endothelial GF (VEGF), are encapsulated separately in the core and shell domains, respectively, the VEGF release rate is much greater than that of PDGF, and the difference of the cumulative release percentage between the two GFs is about 30% on day 7 with LMW core PLGA and more than 45% with HMW core PLGA. As for the angiogenic potential of MC GFs with human umbilical vein endothelial cells (HUVECs), the fluorescence signal of CD31+ suggests that the angiogenic sprout of ECs is more active in MC‐mediated GF delivery than conventional GF delivery, and this difference is significant, based on the number of capillary branches in the unit area. This study demonstrates that the fabrication of biocompatible C‐S MCs is possible, and that the release control of biomolecules is adjustable. Furthermore, MC‐mediated GFs remain in an active form and can upregulate the angiogenic activity of ECs.
Relationships, learning, and development: A student perspective
Authors: Bernstein‐Yamashiro Beth , Noam Gil G.
Published: April 2013

In data derived from student interviews, students describe how they see teacher‐student relationships function for them in their experience of school, their personal development, and their academic success. These relationships are central to students' ability to feel connected at school and to their emerging identities. Students describe how certain teachers are able to reach out to them personally, enabling them to access curriculum and build a positive personal mentoring connection to an adult. Students also explain how being able to rely on relationships with their teachers helps them cope with the many emotional challenges they face as adolescents.
Establishing and maintaining boundaries in teacher‐student relationships
Authors: Bernstein‐Yamashiro Beth , Noam Gil G.
Published: April 2013

Because schools rarely provide guidelines for teachers that outline how they should conduct personal relationships with students, teachers must wrestle individually with how to establish, communicate, and maintain clear boundaries in their interactions. As schools work to become more personal environments, school administrators will need to help teachers understand their roles as close advisors and mentors to students, while drawing and maintaining clear and obvious boundaries within these relationships. Students have clear ideas on how they prefer their teachers to interact with them and what feels comfortable in these relationships. Teachers also discuss from experience how they have managed to find comfortable ways to delimit relationships and continue to be effective mentors for students.
A Process Model for Approximating the Production Costs of the Fermentative Synthesis of Sophorolipids
Authors: Ashby Richard D. , McAloon Andrew J. , Solaiman Daniel K. Y. , Yee Winnie C. , Reed Marshall
Published: April 2013

Sophorolipids are microbial glycolipids that possess surfactant‐type properties. Sophorolipids have been tested successfully in a number of potential industrial and niche applications but are generally acknowledged to require higher production costs when compared to petroleum‐based surfactants. The objective of this study was to develop a process economic model for the fermentative synthesis of sophorolipids using contemporary process simulation software and current reagent, equipment, and supply costs, following current production practices. Glucose (Glc) and either high oleic sunflower oil (HOSO) or oleic acid (OA) were used as feedstocks and the annual production capacity of the plant was set at 90.7 million kg/year with continuous operation of 24 h a day for 330 days per year. Major equipment costs were calculated to be US$17.1 million but other considerations such as capital, labor, material and utilities costs were also included. The single greatest contributor to the overall production/operating cost was raw materials, which accounted for 89 and 87 % of the total estimated production expenditures for the HOSO and OA‐based fermentations, respectively. Based on this model and yields of 100 g/L, the cost of large‐scale sophorolipid synthesis via fermentation from Glc:HOSO was calculated to be US$2.95/kg ($1.34/lb) and from Glc:OA to be US$2.54/kg ($1.15/lb). The model is flexible and can be adjusted to reflect changes in capital, production and feedstock costs as well as changes in the type of feedstocks used.
Synthesis and Characterization of Acetylated and Stearylyzed Soy Wax
Authors: Yao Linxing , Lio JunYi , Wang Tong , Jarboe Darren H.
Published: April 2013

A solvent‐free synthesis method was developed for incorporating acetyl and hydroxy groups and long‐chain fatty alcohol in fully hydrogenated soybean oil (FHSO) to produce a wax to be used as beeswax or paraffin substitutes in packaging and coatings. FHSO was reacted with stearyl alcohol and triacetin at 140–150 °C for 2 h, and the reaction was catalyzed by 0.018 wt% sodium methoxide. The addition of alcohol increased the reaction yield and the melting point of the final wax by 9 and 25 %, respectively, compared to the wax produced from the reaction of FHSO and triacetin alone. The effects of the ratio of stearyl alcohol and triacetin to FHSO on the textural properties of the modified soy wax were examined. The reaction of FHSO:stearyl alcohol:triacetin at a molar ratio of 9:7:15 produced a wax that was 1.2 and 2.4 times harder than beeswax and FHSO, respectively, but 1.7 times softer than a commercial grade paraffin wax. This modified soy wax comprised 75 % acetylated glycerol esters including diacetylmonoacylglycerides (31 %), monoacetylmono‐ (12 %) and diacylglycerides (32 %), and 25 % non‐acetylated molecules including wax ester (14 %), and acylglycerides (11 %). The acetylated soy wax had high cohesiveness and did not break under compression.
Crossing the Line: Local Ethnic Geography and Voting in Ghana
Authors: ICHINO NAHOMI , NATHAN NOAH L.
Published: April 2013

Theories of instrumental ethnic voting in new democracies propose that voters support co-ethnic politicians because they expect politicians to favor their co-ethnics once in office. But many goods that politicians deliver to voters are locally nonexcludable in rural areas, so the local presence of an ethnic group associated with a politician should affect a rural voter's assessment of how likely she is to benefit from that politician's election. Using geocoded polling-station–level election results alongside survey data from Ghana, we show that otherwise similar voters are less likely to vote for the party of their own ethnic group, and more likely to support a party associated with another group, when the local ethnic geography favors the other group. This result helps account for the imperfect correlation between ethnicity and vote choice in African democracies. More generally, this demonstrates how local community and geographic contexts can modify the information conveyed by ethnicity and influence voter behavior.
Effect of glucocorticoids on nasal polyposis, with detection of inflammatory response by measurement of nitric oxide levels in nasal polyp tissue
Authors: Bülbül T , Bülbül Ö Gümüştekin , Güçlü O , Bilsel A Serpil , Gürsan S Önal
Published: April 2013

Objective:

To investigate endoscopic staging, and nitric oxide levels in the polyp tissue, in patients with nasal polyposis undergoing glucocorticoid therapy.

Methods:

Nasal polyposis was evaluated using endoscopic staging and measurement of polyp tissue nitric oxide levels (chemiluminescence method). Forty-five nasal polyposis patients received either nasal therapy (n = 15), oral therapy (n = 15) or combined therapy (n = 15). Pre-treatment and post-treatment staging and nitric oxide levels were evaluated.

Results:

Endoscopic grading indicated significant post-treatment staging improvements in the oral (p = 0.016) and combined (p = 0.016) groups. Post-treatment staging differed significantly between the three groups (p = 0.041), with greater improvements in the oral and combined groups. All groups showed significantly lower post-treatment nitric oxide levels, compared with baseline, but post-treatment levels did not differ significantly between groups. A significant association was found between treatment response and nitric oxide level alteration.

Conclusion:

This study demonstrates the favourable effects of glucocorticoids on nasal polyposis, and alteration in nitric oxide tissue levels post-treatment. Nitric oxide level in nasal polyp tissue could be an indicator of treatment response, and may aid surgical decision-making by detecting cases that probably will not respond to medical treatment.
Lateral undulation of snake robots: a simplified model and fundamental properties
Authors: Liljebäck Pål , Pettersen Kristin Y. , Stavdahl Øyvind , Gravdahl Jan Tommy
Published: April 2013

This paper considers the lateral undulation motion of snake robots. The first contribution of the paper is a model of lateral undulation dynamics developed for control design and stability analysis purposes. The second contribution is an analysis of the simplified model that shows that any asymptotically stabilizing control law for the snake robot to an equilibrium point must be time varying. Furthermore, the analysis shows that a snake robot (with four links) is strongly accessible from almost any equilibrium point, except for certain singular configurations, and that the robot does not satisfy sufficient conditions for small-time local controllability. The third contribution is based on using averaging theory to prove that the average velocity of the robot during lateral undulation will converge exponentially fast to a steady-state velocity which is given analytically as a function of the gait pattern parameters. From the averaging analysis, we also derive a set of fundamental relationships between the gait parameters of lateral undulation and the resulting forward velocity of the snake robot. The paper presents simulation results and results from experiments with a physical snake robot that support the theoretical findings.
QUALITY INDICATORS TO ASSESS A COLORECTAL CANCER PREVENTION PROGRAM
Authors: Serra-Sutton Victoria , Serrano Carmela Barrantes , Carreras Mireia Espallargues
Published: April 2013

Objectives: The aim of this study was to implement a set of indicators to assess the quality of care of a new healthcare model for prevention of colorectal cancer in a high-risk population.

Methods: Information was obtained retrospectively from electronic clinical records, review of documentation, and a survey. The high-risk clinic for colorectal cancer was created in Barcelona (Spain) in 2006. All users at greater risk of colorectal cancer assessed through the new healthcare model were included. Twenty-one indicators were computed using defined formulas and standards. Logistic regression models were computed to analyze factors related to adherence to the screening and surveillance prevention strategies.

Results: A total of 1,275 users were included. Eight of seventeen indicators reached the quality standard (80 percent structure, 50 percent process, and 17 percent outcome), whereas four indicators did not have a previously defined standard. The overall adherence to the screening and surveillance program was 67 percent. Users aged 59 and older had almost two times greater probabiblity (95 percent confidence interval [CI], 1.3–3.1) of adherence than younger users; users with surveillance colonoscopies presented a 7.4 times (95 percent CI, 4.6–11.7) greater probability of adherence than those with screening colonoscopies.

Conclusions: The indicators have been shown to be feasible and valid tools to identify areas of improvement in this new model, such as information systems, continuity of care, and communication among professionals. Because this was the first time these indicators were applied to assess the high-risk clinic for colorectal cancer, further implementation is required to improve the interpretability of results.
From strategic ambiguity to technical reference points in the Antarctic krill fishery: the worst journey in the world?
Authors: HILL SIMEON L.
Published: April 2013

The goals of ecosystem based management (EBM) are strategically ambiguous, meaning that they require interpretation to identify objectives for ecosystem state. Ecosystem states that are useful for achieving such objectives are known as reference points. Soft reference points specify both a state and a probability of the ecosystem being in that state. They are used with simulation models to identify management measures for which the risk of the ecosystem entering an undesirable state is below a specified level. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is responsible for the EBM of Antarctic krill fisheries. CCAMLR used soft reference points for the krill stock in the Scotia Sea and southern Drake Passage to set a regional catch limit. However, this catch limit needs spatial subdivision to protect predators from localized depletion. Model-based evaluations of different options for subdividing the catch limit used illustrative reference points to assess the depletion risk to multiple predators. This study demonstrates that the apparent risk is sensitive to the choice of reference point and method for aggregating modelled predators. EBM practitioners and stakeholders need to be aware that these factors could therefore bias comparisons of management measures. Nonetheless, qualitative distinctions between different spatial subdivision options are relatively consistent except at high levels of aggregation and extreme reference points. This study also demonstrates a lack of generality in the relationship between current and future ecosystem state. Thus, the EBM goal of maintaining ecosystem resilience implies different reference points for the current state of different ecosystem components. Despite early progress in defining soft reference points for the krill stock, CCAMLR has not yet defined reference points for krill predators. Structured dialogue aimed at identifying collective objectives might be necessary to achieve further progress in CCAMLR and other EBM organizations.
A review of bovine tuberculosis at the wildlife–livestock–human interface in sub-Saharan Africa
Authors: De GARINE-WICHATITSKY M. , CARON A. , KOCK R. , TSCHOPP R. , MUNYEME M. , HOFMEYR M. , MICHEL A.
Published: April 2013

Infection of wild animals by bovine tuberculosis (bTB) is raising concern worldwide. This article reviews the current epidemiological situation, risk of emergence and control options at the wildlife–livestock–human interface in sub-Saharan Africa. In livestock, bTB has been confirmed in the majority of countries from all parts of the continent. Wildlife infection is confirmed in seven countries from southern and eastern Africa, apparently spreading in the southern Africa region.Mycobacterium bovishas been isolated from 17 wild mammal species, although only four are suspected to play a role as maintenance host. Zoonotic risks are a concern, but no direct spillover from wildlife to humans has been documented, and no case of bTB spillback from wildlife to livestock has been confirmed. In this paper we assess the main risk factors of bTB spillover at the wildlife–livestock–human interface and suggest several research themes which could improve the control of the disease in the African context.
Seroepidemiology ofToxoplasma gondiiinfection in the Israeli population
Authors: MARKOVICH M. PERRY , SHOHAT T. , RIKLIS I. , AVNI R. , YUJELEVSKI-ROZENBLIT D. , BASSAL R. , COHEN D. , RORMAN E.
Published: April 2013

Toxoplasmosis seroprevalence varies considerably between countries. We studied the seoprevalence ofToxoplasma gondiiIgG antibodies in a national sample of the Israeli population; 2794 sera were tested. The highest age-adjusted seroprevalence rate was in Arabs (non-Bedouins) (60·4%), significantly higher compared to the rate in Jews (19·9%) and Bedouins (27·5%) (P < 0·01). There were no significant gender differences. Seropositivity increased with age in all population groups. For Jews, seropositivity was associated with place of birth and socioeconomic status. A finding of low seroprevalence rate in Bedouins despite their poor living conditions and close contact with livestock is surprising, and might be attributed to the dry and hot climate conditions in their area of residence. In women of reproductive age the seroprevalence was 15·1% in Jews, 25·4% in Bedouins and 72·3% in Arabs (non-Bedouins). Thus, the majority of pregnant women are susceptible to primary infection withT. gondii, and the risk for congenital toxoplasmosis remains high.
Enhanced tunable performance of high Q-factor BaxSr1−xTiO3 film bulk acoustic wave resonators
Authors: Vorobiev Andrei , Gevorgian Spartak
Published: April 2013

Emerging intrinsically tunable film bulk acoustic wave(BAW) resonators allow the development of new generation reconfigurable and agile microwave circuits. In this paper, we demonstrate the enhancement of tunable performance of the high Q-factor BaxSr1−xTiO3 BAW – solidly mounted resonators (BAW–SMR) by varying Ba concentration. The Ba0.5Sr0.5TiO3 BAW–SMR reveal tunability of series resonance frequency up to 2.4%, electromechanical coupling coefficient up to 7.5% and rather high Q-factor, up to 250 at 5.3 GHz. Correlations between the measured electroacoustic parameters are analyzed using the theory of dc field-induced piezoelectric effect in paraelectric phase ferroelectrics. Higher coupling coefficient and tunability of resonance frequency of the Ba0.5Sr0.5TiO3 BAW–SMR are associated with higher tunability of permittivity. Strong anisotropy in field-induced piezoelectric effect is predicted with highest coupling coefficient in (001) direction of the BaxSr1−xTiO3 films. It is also shown that the tunability of series resonance frequency of Ba0.5Sr0.5TiO3 BAW–SMR is limited by relatively high and negative nonlinear electrostriction coefficient which is found to be m ≈ −4·1010 m/F. The BAW–SMR Q-factor is limited significantly by extrinsic acoustic loss associated with wave scattering at reflection from relatively rough top interface. The results of analysis show possible ways of further improvement of the performance of tunable BAW–SMR.
Reference Correlation of the Thermal Conductivity of n-Heptane from the Triple Point to 600 K and up to 250 MPa
Authors: Assael M. J. , Bogdanou I. , Mylona S. K. , Huber M. L. , Perkins R. A. , Vesovic V.
Published: April 2013

This paper contains new, representative reference equations for the thermal conductivity of n-heptane. The equations are based in part upon a body of experimental data that have been critically assessed for internal consistency and for agreement with theory whenever possible. In the case of the dilute-gas thermal conductivity, a theoretically based correlation was adopted in order to extend the temperature range of the experimental data. Moreover, in the critical region, the experimentally observed enhancement of the thermal conductivity is well represented by theoretically based equations containing just one adjustable parameter. The correlations are applicable for the temperature range from the triple point to 600 K and pressures up to 250 MPa. The overall uncertainty (considered to be estimates of a combined expanded uncertainty with a coverage factor of 2) of the proposed correlation is estimated, for pressures less than 250 MPa and temperatures less than 600 K, to be less than 4%.
Secondary relaxation processes in binary glass formers: Emergence of “islands of rigidity”
Authors: Micko B. , Tschirwitz C. , Rössler E. A.
Published: April 2013

In addition to the primary α-process, some neat glass formers show a well resolved secondary β-process (type-B) or solely an excess wing (type-A). We investigate two binary glass forming systems composed of a type-A and a type-B component. 2H nuclear magnetic resonance (NMR) spectroscopy is selectively applied to the type-B component in order to characterize the β-process over a large range of mole fractions x in the glassy state. We demonstrate that for x ≳ 0.75 the apparent relaxation strength is constant, i.e., all molecules of type-B participate in the β-process and the time constant τβ(T) is independent of concentration. For x < 0.75, however, the apparent relaxation strength decreases abruptly, which we interpret in terms of population: below this concentration a fraction ξ of type-B molecules still exhibits essentially the β-process of the neat system (in terms of time scale and mechanism), while others have been immobilized. The arise of such a scenario is verified by 2D and spin-lattice relaxation 2H NMR techniques. In selective 2H NMR experiments on the type-A component we observe a contribution to the β-process of the type-B molecules at medium concentrations. The latter finding and the rather sharp threshold occurring at x ≈ 0.75 may indicate that the β-process is a cooperative process.
Effects of electric field on the entropy, viscosity, relaxation time, and glass-formation
Authors: Johari G. P.
Published: April 2013

By using the known formalism for the effect of an externally applied electric field, E, on thermodynamics of a dielectric material, we calculated the field-induced configurational entropy factor, $\Delta S_{conf}^E /E^2$ΔSconfE/E2, of 50 dipolar liquids, including those whose static permittivity, ɛs, decreases on cooling. The field induced change, $\Delta S_{conf}^E$ΔSconfE, is found to be experimentally detectable only when E is on the order of 105 V/cm, a value less than the dielectric breakdown field strength of some liquids but in the range of nonlinear dielectric response. We argue that the dielectric response is formally nonlinear already for E > 0, and then show that the difference between the Langevin-function and the extrapolated linear response is < 0.15% for E in the 105 V/cm range. Therefore, such high E values may be used to estimate $\Delta S_{conf}^E$ΔSconfE. We conclude that (i) for E in the 105 V/cm range, $\Delta S_{conf}^E$ΔSconfE is high enough to produce a measurable change in the viscosity and relaxation time of some ultraviscous liquids with prominent dipolar interactions, thereby changing their glass formation temperature, and (ii) application of E would reversibly transform, isothermally, some liquids to glass, and transform some glasses to liquid. Finally, we suggest that the effect of E can be used to determine the merits of the models for non-Arrhenius kinetics.
Crystal structure and charge transport properties of poly(arylene-ethynylene) derivatives: A DFT approach
Authors: Garzón Andrés , Granadino-Roldán José M. , García Gregorio , Moral Mónica , Fernández-Gómez Manuel
Published: April 2013

In the present study, a series of crystalline poly(arylene-ethynylene) copolymers containing phenylethynylene and 2,5-dialkoxy-phenylethynylene units together with 1,3,4-thiadiazole rings has been modeled by means of periodic calculations. Optimized three-dimensional polymeric structures show interchain distances that are consistent with the experimental values reported for a related polymer. It has also been observed that the presence of pendant alkoxy chains brings on both a further flattening and a separation of the coplanar chains. This fact is linked to a decrease of the interchain cofacial distance. The electron transport character of the polymer crystal structures was assessed through Marcus theory. Electronic coupling between neighboring polymer chains is most influenced by the presence of alkoxy chains giving rise to an expectable enhancement of the electron hopping mobility.
The local structure, magnetic, and transport properties of Cr-doped In2O3 films
Authors: Wang Shiqi , An Yukai , Feng Deqiang , Wu Zhonghua , Liu Jiwen
Published: April 2013

Cr-doped In2O3 films were deposited on Si (100) substrates by RF-magnetron sputtering technique. The local structure, magnetic, and transport properties of films are investigated by X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption fine structure, Hall effect, R-T, and magnetic measurements. Structural analysis clearly indicates that Cr ions substitute for In3+ sites of the In2O3 lattice in the valence of +2 states and Cr-related secondary phases or clusters as the source of ferromagnetism is safely ruled out. The films with low Cr concentration show a crossover from semiconducting to metallic transport behavior, whereas only semiconducting behavior is observed in high Cr concentration films. The transport property of all films is governed by Mott variable range hopping behavior, suggesting that the carriers are strongly localized. Magnetic characterizations show that the saturated magnetization of films increases first, and then decreases with Cr doping, while carrier concentration nc decreases monotonically, implying that the ferromagnetism is not directly induced by the mediated carriers. It can be concluded the ferromagnetism of films is intrinsic and originates from electrons bound in defect states associated with oxygen vacancies.
Negative refraction and backward wave in chiral mediums: Illustrations of Gaussian beams
Authors: Chern Ruey-Lin , Chang Po-Han
Published: April 2013

We investigate the phenomena of negative refraction and backward wave in chiral mediums, with illustrations of Gaussian beams. Due to symmetry breaking intrinsic in chiral mediums, there exist two circularly polarized eigenwaves with different wave vectors. The two waves begin to split from each other as the chirality parameter increases from zero. The right (left)-handed circularly polarized wave tends to move toward (away from) the normal to the interface. As the chirality exceeds a critical value, the left-handed wave is flipped to the other side of the interface normal, that is, negatively refracted, and becomes a backward wave. These features are illustrated with Gaussian beams based on Fourier integral formulations. The special condition of perfectly negative refraction in chiral mediums is also discussed.
Magnetic field-controlled femtosecond pulse shaping by magnetoplasmonic crystals
Authors: Vabishchevich P. P. , Frolov A. Yu. , Shcherbakov M. R. , Grunin A. A. , Dolgova T. V. , Fedyanin A. A.
Published: April 2013

Femtosecond-scale magnetic field-controlled shaping of 200 fs laser pulses reflected from a one-dimensional magnetoplasmonic crystal is experimentally demonstrated. Magnetic field-induced modification of the pulse shape is revealed by measuring the second-order intensity correlation function (CF) of femtosecond pulses reflected from the sample. The sign of the magnetic contribution to the CF is reversed within the pulse. Such temporal shaping of the pulses is attributed to modification of the Fano-type surface plasmon spectral response function under magnetization of the sample in the Voigt configuration.
Enhancement of thermopower and thermoelectric performance through resonant distortion of electronic density of states of β-Zn4Sb3 doped with Sm
Authors: Wang Q. Q. , Qin X. Y. , Li D. , Zou T. H.
Published: April 2013

Thermoelectric properties of Sm-doped compounds β-(Zn1−xSmx)4Sb3 (x = 0, 0.001, 0.002, and 0.003) (at 300-615 K) were investigated. The results indicate that Sm doping causes the resonant distortion of density of states of β-Zn4Sb3, as manifested by almost 2-fold increase in effective mass md* of β-Zn4Sb3, which results in ∼40 μV/K increase of the thermopower for all the doped samples. Besides, thermal conductivity decreases substantially by Sm doping. As a result, figure of merit ZT of β-(Zn0.008Sm0.002)4Sb3 is ∼53% larger than that of the un-doped one and reaches 1.1 at 615 K, suggesting that Sm doping is an effective approach to improve ZT of β-Zn4Sb3.
Mask assisted fabrication of nanoislands of BiFeO3 by ion beam milling
Authors: Morelli A. , Johann F. , Schammelt N. , McGrouther D. , Vrejoiu I.
Published: April 2013

We report on a low-damage method for direct and rapid fabrication of arrays of epitaxial BiFeO3 (BFO) nanoislands. An array of aluminium dots is evaporated through a stencil mask on top of an epitaxial BiFeO3 thin film. Low energy focused ion beam milling of an area several microns wide containing the array-covered film leads to removal of the bismuth ferrite in between the aluminium-masked dots. By chemical etching of the remaining aluminium, nanoscale epitaxial bismuth ferrite islands with diameter ∼250 nm were obtained. Piezoresponse force microscopy showed that as-fabricated structures exhibited good piezoelectric and ferroelectric properties, with polarization state retention of several days.
Ohmic contact formation between metal and AlGaN/GaN heterostructure via graphene insertion
Authors: Sung Park Pil , Reddy Kongara M. , Nath Digbijoy N. , Yang Zhichao , Padture Nitin P. , Rajan Siddharth
Published: April 2013

A simple method for the creation of Ohmic contact to 2D electron gas in AlGaN/GaN high electron-mobility transistors using Cr/graphene layer is demonstrated. A weak temperature dependence of this Ohmic contact observed in the range 77 to 300 K precludes thermionic emission or trap-assisted hopping as possible carrier-transport mechanisms. It is suggested that the Cr/graphene combination acts akin to a doped n-type semiconductor in contact with AlGaN/GaN heterostructure, and promotes carrier transport along percolating Al-lean paths through the AlGaN layer. This use of graphene offers a simple method for making Ohmic contacts to AlGaN/GaN heterostructures, circumventing complex additional processing steps involving high temperatures. These results could have important implications for the fabrication and manufacturing of AlGaN/GaN-based microelectronic and optoelectronic devices/sensors of the future.
Analysis of amorphous indium-gallium-zinc-oxide thin-film transistor contact metal using Pilling-Bedworth theory and a variable capacitance diode model
Authors: Kiani Ahmed , Hasko David G. , Milne William I. , Flewitt Andrew J.
Published: April 2013

It is widely reported that threshold voltage and on-state current of amorphous indium-gallium-zinc-oxide bottom-gate thin-film transistors are strongly influenced by the choice of source/drain contact metal. Electrical characterisation of thin-film transistors indicates that the electrical properties depend on the type and thickness of the metal(s) used. Electron transport mechanisms and possibilities for control of the defect state density are discussed. Pilling-Bedworth theory for metal oxidation explains the interaction between contact metal and amorphous indium-gallium-zinc-oxide, which leads to significant trap formation. Charge trapping within these states leads to variable capacitance diode-like behavior and is shown to explain the thin-film transistor operation.
Flexible and transparent graphene-based loudspeakers
Authors: Xu S. C. , Man B. Y. , Jiang S. Z. , Chen C. S. , Yang C. , Liu M. , Gao X. G. , Sun Z. C. , Zhang C.
Published: April 2013

Flexible and transparent graphene films have been fabricated via chemical vapor deposition method, and an extremely thin and lightweight loudspeaker was obtained by transferring the graphene films on both side of the polyvinylidene fluoride film. Once fed by sound frequency electric field, the graphene-based acoustic actuator could emit loud sounds in a wide frequency range. Such film loudspeakers are transparent, flexible, magnet-free and can be tailored into any shape and size, which have wide potential applications in fabricating new type of transparent and flexible devices.
Characterization of anti-phase boundaries in hetero-epitaxial polar-on-nonpolar semiconductor films by optical second-harmonic generation
Authors: Lei Ming , Price J. , Wang Wei-E , Wong Man Hoi , Droopad Ravi , Kirsch Paul , Bersuker G. , Downer M. C.
Published: April 2013

Compound semiconductor layers (e.g., GaAs) grown on elemental semiconductor substrates (e.g., Si, Ge) are vulnerable to formation of anti-phase boundary (APB) defects. We show that optical second-harmonic generation (SHG) signals from APB-rich epi-layers are orders of magnitude weaker than from APB-free samples. Moreover, scanning SHG images of APB-rich layers reveal microstructure lacking in APB-free layers. We attribute these findings to the sign reversal of the second-order nonlinear optical susceptibility χijk(2) between neighbouring anti-phase domains within the incident laser spot. In contrast, SHG is insensitive to threading dislocations. Thus, SHG can identify APBs selectively and non-invasively for advanced MOSFET device applications.
Cation disorder as the major electron scattering source in crystalline InGaZnO
Authors: Kang Youngho , Cho Youngmi , Han Seungwu
Published: April 2013

We theoretically investigate the electron transport mechanism in crystalline In-Ga-Zn oxides using the semi-classical transport theory. The site disorder of Ga and Zn atoms is treated based on the virtual crystal approximation. The valence difference between Ga3+ and Zn2+, modeled by screened Coulomb potential, plays a critical role in determining the total electron mobility. The temperature and carrier-density dependences of the calculated electron mobility are in excellent agreement with experimental data. The unusual behavior of electron mobility is explained based on the energy-dependent relaxation time and underlying band structure.
A localized transition in the size variation of circular DNA in nanofluidic slitlike confinement
Authors: Strychalski Elizabeth A. , Stavis Samuel M. , Geist Jon
Published: April 2013

We report strong evidence for a localized transition in the size variation of circular DNA between strong and moderate regimes of slitlike confinement. A novel and rigorous statistical analysis was applied to our recent experimental measurements of DNA size for linear and circular topologies in nanofluidic slits with depths around ≈ 2p, where p is the persistence length. This empirical approach revealed a localized transition between confinement regimes for circular DNA at a slit depth of ≈ 3p but neither detected nor ruled out the possibility for such a transition for linear DNA. These unexpected results provide the first indication of the localized influence of polymertopology on size variation in slitlike confinement. Improved understanding of differences in polymer behavior related to topology in this controversial and relevant system is of fundamental importance in polymer science and will inform nanofluidic methods for biopolymeranalysis.
SMS experience and textisms in young adolescents
Authors: Bernicot Josie , Volckaert-Legrier Olga , Goumi Antonine , Bert-Erboul Alain
Published: April 2013

The aim of this paper was to study the characteristics of SMSes in a population for which there is currently only limited data: young adolescents (girls and boys) between 11 and 12 years of age. The analysis focused on a corpus of 4,524 SMSes sent by 19 informants in everyday real-life situations over a one-year period. At the beginning of the study, the participants were complete novices. This study sets forth a new analysis grid which distinguishes between two categories of textisms which were defined based on the following cognitive processes: (a) textisms which are consistent with the traditional written code of grapheme–phoneme correspondence and (b) textisms which break with this traditional code. On the whole, the density of textisms was .52 and .26, respectively, for each kind of textism. The results showed an increase in the density of textisms with SMS experience (from month 1 to month 12), but also a variation depending upon the type of textism and the gender of the texter. For boys, the density of both types of textisms increased with SMS experience, while for girls, the density of textisms only increased for textisms which broke with the code. The results were interpreted in terms of the construction of an SMS register with specific linguistic markers resulting from a different use of traditional writing rules or the use of inventions as compared to traditional writing.
Automatic or Controlled Writing?
Authors: Combes Céline , Volckaert-Legrier Olga , Largy Pierre
Published: April 2013

The objective of this study was to attempt to distinguish the various processes of producing SMS spelling forms. The production of these different spelling forms was compared by means of an experimental paradigm: the dual task. This paradigm aimed at identifying the attentional resources necessary for the process of producing SMS spelling. Another way in which to address the degree of automation of these production processes was to compare SMS productions in terms of the level of SMS writing expertise. The results of this study demonstrated that the spelling forms produced in SMS language (eSMS), and therefore their production process, differ according to the degree of SMS writing expertise and the attention that the participants are able to devote to the SMS writing task. The results confirm that SMS writing represents a cognitive cost for novice texters and tends to become automatic as the users acquire expertise.
SMS communication as plurilingual communication
Authors: Morel Étienne , Bucher Claudia , Pekarek Doehler Simona , Siebenhaar Beat
Published: April 2013

The use of more than one language in SMS communication is widespread, yet has remained relatively underexplored in the existing research. In this paper we ask: What methodological and conceptual tools are needed for empirically investigating code-switching in large databases of SMS communication? We show that the investigation of SMS communication calls for an adaptation of the conceptual and the methodological apparatus of classical code-switching studies, which have been typically concerned with the analysis of spoken, mostly interactional, data. We argue for a broad understanding of code-switching that comprises switching between natural languages and language varieties along with style shifts as well as switching between language and other semiotic systems (ideographic switching). We also document, as a key feature of SMS communication, hybrid forms of language use that blur the boundaries between what we commonly call languages (e.g. homographs, mixed spellings or allogenisms), and we suggest that these possibly indicate that SMS communication has become one site where the tension between localized and globalized social practices is played out. The study presented here is part of an inter-university research project, entitled “SMS communication in Switzerland: Facets of linguistic variation in a multilingual country”, based on a corpus of 26,000 authentic messages collected between 2009 and 2011.
The psychosocial impact of child labour in Jordan: A national study
Authors: Al‐Gamal Ekhlas , Hamdan‐Mansour Ayman M. , Matrouk Reema , Nawaiseh Maram Al
Published: April 2013

The purpose of this study was to identify the psychosocial impact of child labour in Jordan, distinguishing between the impact on working school children, nonworking school children and working and nonschooled children. More than 351 million children across the world work. Emotional, behavioral and psychiatric problems in working children are a considerable public health problem in developing countries. A descriptive, comparative, cross‐sectional design was used in this study. All data were collected in 2010. A total of 4008 children aged six to 16 years were interviewed. Of these, 2093 (52.2%) were nonworking school children, 896 (22.4%) working school children, and 1019 (25.4%) working and nonschooled children. Working school children reported psychosocial problems more often than working and nonschooled children. Child labour has a negative impact on children's psychosocial health and development. These findings indicate that psychoeducational support and problem‐solving programs help children to cope better with the consequences of their work and study. More effort is needed to reduce children's involvement in labour. Understanding the impact of work on child mental and social health is essential to inform policy and future research as well as to improve the lives of children.
What Is the Relative Importance of Phytoplankton and Attached Macroalgae and Epiphytes to Food Webs on Offshore Oil Platforms?
Authors: Daigle Sara T. , Fleeger John W. , Cowan James H. , Pascal Pierre-Yves
Published: April 2013

Offshore oil platforms function as artificial reefs, but little is known about the food webs that fuel platform-dwelling biota. Here, we use carbon and nitrogen isotopes in tissues of biota from two offshore oil platforms to estimate the importance of phytoplankton and platform-associated macroalgae and epiphytic microalgae to the diets of platform-dwelling consumers. Although the consumption of macroalgae was indicated for small, mobile consumers including crabs, amphipods, and harpacticoid copepods, both a Bayesian mixing model and temporal changes in isotope composition identified phytoplankton as the most important basal resource for these consumers. Sessile suspension-feeding barnacles and oysters consumed phytoplankton and epiphytes, and probably redirected large amounts of pelagic production to other consumers. Secondary consumers including syllid polychaetes and the blennies, Molly Miller Scartella cristata and Tessellated Blenny Hypsoblennius invemar, exhibited a distinct contribution from epiphytes although large ranges in all potential basal resources were observed. Elemental and isotope analysis of the gut contents of individuals indicated that the nektonic Gray Triggerfish Balistes capriscus was omnivorous, directly consuming reef-derived macroalgae and epiphytes as well as animal tissue. Although we found that reef-derived resources entered benthic and nektonic food webs surrounding platforms, phytoplankton was the dominant basal resource fueling platform-dwelling communities at the time of our study, and no consumer studied specialized on a diet of red macroalgae. If these findings are generally representative, platform-derived benthic algae would not be integral to food-web function on artificial reefs, and reef function should be similar in areas both favorable to and unfavorable to in situ algal growth.

Received April 20, 2012; accepted January 31, 2013
Panta rhei: The APC/C at steady state
Authors: Primorac Ivana , Musacchio Andrea
Published: April 2013

The anaphase-promoting complex or cyclosome (APC/C) is a conserved, multisubunit E3 ubiquitin (Ub) ligase that is active both in dividing and in postmitotic cells. Its contributions to life are especially well studied in the domain of cell division, in which the APC/C lies at the epicenter of a regulatory network that controls the directionality and timing of cell cycle events. Biochemical and structural work is shedding light on the overall organization of APC/C subunits and on the mechanism of substrate recognition and Ub chain initiation and extension as well as on the molecular mechanisms of a checkpoint that seizes control of APC/C activity during mitosis. Here, we review how these recent advancements are modifying our understanding of the APC/C.
A chain of π-stacked molecules in 4-(2-chlorophenyl)pyrrolo[1,2-a]quinoxaline and a hydrogen-bonded sheet in (4RS)-4-(1,3-1,3-benzodioxol-6-yl)-4,5-dihydropyrrolo[1,2-a]quinoxaline
Authors: Castillo Juan C. , Abonía Rodrigo , Cobo Justo , Glidewell Christopher
Published: April 2013

In the molecule of 4-(2-chlorophenyl)pyrrolo[1,2-a]quinoxaline, C17H11ClN2, (I), the bond lengths are consistent with electron delocalization in the two outer rings of the fused tricyclic system, with a localized double bond in the central ring. The molecules of (I) are linked into chains by a π–π stacking interaction. In (4RS)-4-(1,3-benzodioxol-6-yl)-4,5-dihydropyrrolo[1,2-a]quinoxaline, C18H14N2O2, (II), the central ring of the fused tricyclic system adopts a conformation intermediate between screw-boat and half-chair forms. A combination of N—H...O and C—H...π(arene) hydrogen bonds links the molecules of (II) into a sheet. Comparisons are made with related compounds.
Reliable genotyping of the koala (Phascolarctos cinereus) usingDNAisolated from a single faecal pellet
Authors: Wedrowicz Faye , Karsa Mawar , Mosse Jennifer , Hogan Fiona E.
Published: April 2013

The koala, anAustralian icon, has been added to the threatened species list. Rationale for the listing includes proposed declines in population size, threats to populations (e.g. disease) and loss and fragmentation of habitat. There is now an urgent need to obtain accurate data to assess the status of koala populations inAustralia, to ensure the long‐term viability of this species. Advances in genetic techniques have enabledDNAanalysis to study and inform the management of wild populations; however, sampling of individual koalas is difficult in tall, often remote, eucalypt forest. The collection of faecal pellets (scats) from the forest floor presents an opportunistic sampling strategy, whereDNAcan be collected without capturing or even sighting an individual. ObtainingDNAvia noninvasive sampling can be used to rapidly sample a large proportion of a population; however,DNAfrom noninvasively collected samples is often degraded. Factors influencingDNAquality and quantity include environmental exposure, diet and methods of sample collection, storage andDNAisolation. ReducedDNAquality and quantity can introduce genotyping errors and provide inaccurateDNAprofiles, reducing confidence in the ability of such data to inform management/conservation strategies. Here, we present a protocol that produces a reliable individual koala genotype from a single faecal pellet and highlight the importance of optimizingDNAisolation and analysis for the species of interest. This method could readily be adapted for genetic studies of mammals other than koalas, particularly those whose diet contains high proportions of volatile materials that are likely to induceDNAdamage.