bluuebunny/crossref_metadata_2025 huggingface dataset:
A Qualitative Exploration of Cyber-Bystanders and Moral Engagement
Authors: Price Deborah , Green Deborah , Spears Barbara , Scrimgeour Margaret , Barnes Alan , Geer Ruth , Johnson Bruce
Published: September 2013

Studies have found that moral disengagement plays a significant role in the continuation of bullying situations (Bonanno, 2005); however, the moral stance of cyber-bystanders — those who witness online bullying — is not yet clear. While research into traditional face-to-face bullying reported that peers would probably or certainly intervene to support victims in 43% of cases (Rigby & Johnson, 2006) actual intervention is reportedly much less (Atlas & Pepler, 1998; Craig & Pepler, 1997). Little is known, however, about the attitudes and behaviours of bystanders or witnesses when online, or their probable intentions to intervene. This study employed three digital animations of typical cyberbullying scenarios to explore young people's views of cyber-bystanders. Youth from Years 8–12 (mean age 15.06,N= 961) from one metropolitan secondary school in Adelaide, South Australia, completed an online survey after watching vignettes. To shed light on the rationale and thinking behind their understanding of bystanders and moral dis/engagement when online, this article reports on the qualitative responses from young people in relation to one of these animations/vignettes. The findings suggest that young people perceive cyber-bystanders to have the capacity to morally engage in cyberbullying incidents; however, there are various barriers to their active positive engagement. The implications can inform educators and school counsellors about possible ways to support students to intervene when they witness cyberbullying.
Postprandial response of plasma IL-6 to isoenergetic meals rich in casein or potato singly and combined in obese women
Authors: Manning Patrick J. , Sutherland Wayne H. F. , de Jong Sylvia A. , Ryalls Anne R. , Berry Elizabeth A.
Published: September 2013

Milk consumption decreases inflammatory stress in overweight and obese subjects. Casein is the major protein in milk and enhances the secretion of insulin that has anti-inflammatory activity. The aim of the present study was to compare the acute effect of meals rich in casein and carbohydrate and a combination of both nutrients on postprandial plasma concentrations of IL-6, a marker of inflammation, in obese women. A total of twenty-five obese women aged 38–68 years consumed isoenergetic meals rich in potato (POT) or casein (CA) or a combination of both these meals (POT + CA), in random order in a cross-over trial. After an overnight fast, blood samples were collected before and at 1 and 4 h after the meals and circulating concentrations of IL-6, glucose, insulin and NEFA were measured. Plasma IL-6 concentrations increased significantly (P < 0·001) during 4 h after the meals. The AUC of postprandial IL-6 concentrations was not significantly (P = 0·77) different among the meals. Postprandial serum insulin concentration AUC was significantly higher during the POT + CA meal compared with the POT meal (P = 0·001) and the CA meal (P < 0·05), which in turn was significantly higher than the POT meal (P < 0·05). These data show that while ingestion of CA alone or combined with POT acutely increases circulating insulin concentrations, it does not appreciably alter the postprandial increase in plasma IL-6 concentrations in obese women.
Effects of dietary plant meal and soya-saponin supplementation on intestinal and hepatic lipid droplet accumulation and lipoprotein and sterol metabolism in Atlantic salmon (Salmo salarL.)
Authors: Gu Min , Kortner Trond M. , Penn Michael , Hansen Anne Kristine , Krogdahl Åshild
Published: September 2013

Altered lipid metabolism has been shown in fish fed plant protein sources. The present study aimed to gain further insights into how intestinal and hepatic lipid absorption and metabolism are modulated by plant meal (PM) and soya-saponin (SA) inclusion in salmon feed. Post-smolt Atlantic salmon were fed for 10 weeks one of four diets based on fishmeal or PM, with or without 10 g/kg SA. PM inclusion resulted in decreased growth performance, excessive lipid droplet accumulation in the pyloric caeca and liver, and reduced plasma cholesterol levels. Intestinal and hepatic gene expression profiling revealed an up-regulation of the expression of genes involved in lipid absorption and lipoprotein (LP) synthesis (apo, fatty acid transporters, microsomal TAG transfer protein, acyl-CoA cholesterol acyltransferase, choline kinase and choline-phosphate cytidylyltransferase A), cholesterol synthesis (3-hydroxy-3-methylglutaryl-CoA reductase) and associated transcription factors (sterol regulatory element-binding protein 2 and PPARγ). SA inclusion resulted in reduced body pools of cholesterol and bile salts. The hepatic gene expression of the rate-limiting enzyme in bile acid biosynthesis (cytochrome P450 7A1 (cyp7a1)) as well as the transcription factor liver X receptor and the bile acid transporterabcb11(ATP-binding cassette B11) was down-regulated by SA inclusion. A significant interaction was observed between PM inclusion and SA inclusion for plasma cholesterol levels. In conclusion, gene expression profiling suggested that the capacity for LP assembly and cholesterol synthesis was up-regulated by PM exposure, probably as a compensatory mechanism for excessive lipid droplet accumulation and reduced plasma cholesterol levels. SA inclusion had hypocholesterolaemic effects on Atlantic salmon, accompanied by decreased bile salt metabolism.
THE EFFECTS OF ALUMINIUM ON THE PHOTOSYNTHETIC APPARATUS OF TWO RICE CULTIVARS
Authors: JÚNIOR E. M. FONSECA , CAMBRAIA J. , RIBEIRO C. , OLIVA M. A. , OLIVEIRA J. A. , DaMATTA F. M.
Published: September 2013

We aimed to evaluate aluminium (Al) effects on the photosynthetic apparatus of two rice cultivars with contrasting tolerances to Al. Nine-days-old seedlings were exposed to 0 or 1 mM Al for 10 days, and then dry mass, Al and chloroplastidic pigment contents and photosynthetic parameters were determined. Al accumulated mainly in the roots of the Al-treated plants. In the leaves, Al increased only in the sensitive cultivar, but there was no difference between the cultivars in Al-treated plants. The root and leaf dry mass, the net carbon assimilation rate, stomatal conductance and internal CO2 concentration were all reduced in response to Al application, but only in the sensitive cultivar. Both the initial fluorescence and potential photochemical efficiency of photosystem II were unresponsive to the Al treatments, regardless of the cultivar. In the Al-sensitive cultivar, Al provoked significant decreases in the photochemical quenching coefficient, quantum yield of photosystem II electron transport and apparent electron transport rate, in parallel to an unaltered non-photochemical quenching coefficient. All of these parameters remained at the control levels in the tolerant cultivar. The chloroplastidic pigment content increased only in the Al-tolerant cultivar, whereas it remained unaltered after Al treatment in the sensitive cultivar. In conclusion, Al induced stomatal and (most likely) photochemical constraints on photosynthesis but with no apparent signs of photoinhibition in the Al-sensitive cultivar. Despite the similar Al levels of the cultivars, unchanging biomass accumulation or photosynthetic performance in the tolerant cultivar challenged with Al highlights its higher intrinsic ability to cope with Al stress.
Composing and performing in the key stage 3 classroom: a study using multi-trait, multi-method analysis
Authors: Fowler Andrew
Published: September 2013

‘Music is both a creative and a performing art’ (Hallam, 2006, p. 70). Many musicians and music educators maintain that composing and performing, although related, are essentially different aspects of musical activity. In the professional musical sphere, composition and performance are almost invariably separated; academic studies have treated them discretely; GCSE and ‘A’ level specifications assess them distinctly, and many music teachers assess them in the classroom as if they were separate disciplines. It is common practice for students in the lower secondary school in England to work in a more integrated way, however (Philpott, 2001; Major, 2008), composing, performing to the class, and appraising each others’ work. Recently produced assessment guidelines for secondary school music teachers in England (NAME, 2011) encourage this more integrated view, accepting the assumption made by Swanwick and Franca (1999, p. 12) that ‘musical understanding is a broad conceptual dimension’ by considering composing and performing as inter-linked ways of demonstrating and communicating musicality. This study sets out to investigate the links between composing and performing in the secondary school classroom, through peer-rating, teacher rating and students’ self-report attitudinal questionnaires, analysing these using a multi-trait, multi-method technique.

Evidence for convergent validity was found between performing and composing in the classroom, suggesting that they are closely linked and may indeed be related parts of the same trait. This may have implications for the ways in which composing and performing are taught and assessed. A larger-scale study could be undertaken to investigate this further.
Stability for the spherically symmetric Einstein–Vlasov system–a coercivity estimate
Authors: HADŽIĆ MAHIR , REIN GERHARD
Published: September 2013

The stability of static solutions of the spherically symmetric, asymptotically flat Einstein–Vlasov system is studied using a Hamiltonian approach based on energy-Casimir functionals. The main results are a coercivity estimate for the quadratic part of the expansion of the natural energy-Casimir functional about an isotropic steady state, and the linear stability of such steady states. The coercivity bound shows in a quantified way that this quadratic part is positive definite on a class of linearly dynamically accessible perturbations, provided the particle distribution of the steady state is a strictly decreasing function of the particle energy and provided the steady state is not too relativistic. In contrast to the stability theory for isotropic steady states of the gravitational Vlasov-Poisson system the monotonicity of the particle distribution alone does not determine the stability character of the state, a fact which was observed by Ze'ldovitch et al. in the 1960's. The result in an essential way exploits the non-linear structure of the Einstein equations satisfied by the steady state and is not just a perturbation result of the analogous coercivity bounds for the Newtonian case. It should be an essential step in a fully non-linear stability analysis for the Einstein–Vlasov system.
Quorum Exploitation in the American Legislative Experience
Authors: Squire Peverill
Published: September 2013

I examine the exploitation of quorum rules in American legislatures from the colonial era to the present. After documenting changing quorum standards, I examine instances where minorities (and occasionally majorities) have exploited them through disappearing quorums and bolting quorums. This analysis allows me to identify the conditions under which quorum rules have been more easily abused for partisan purposes.
Factors Associated with High-Rise Evacuation: Qualitative Results from the World Trade Center Evacuation Study
Authors: Gershon Robyn R.M. , Qureshi Kristine A. , Rubin Marcie S. , Raveis Victoria H.
Published: September 2013

Introduction:

Due to the fact that most high-rise structures (i.e., >75 feet high, or eight to ten stories) are constructed with extensive and redundant fire safety features, current fire safety procedures typically only involve limited evacuation during minor to moderate fire emergencies. Therefore, full-scale evacuation of high-rise buildings is highly unusual and consequently, little is known about how readily and rapidly high-rise structures can be evacuated fully. Factors that either facilitate or inhibit the evacuation process remain under-studied.

Objective:

This paper presents results from the qualitative phase of the World Trade Center Evacuation Study, a three-year, five-phase study designed to improve our understanding of the individual, organizational, and environmental factors that helped or hindered evacuation from the World Trade Center (WTC) Towers 1 and 2, on 11 September 2001.

Methods:

Qualitative data from semi-structured, in-depth interviews and focus groups involving WTC evacuees were collected and analyzed.

Results:

On the individual level, factors that affected evacuation included perception of risk (formed largely by sensory cues), preparedness training, degree of familiarity with the building, physical condition, health status, and footwear. Individual behavior also was affected by group behavior and leadership. At the organizational level, evacuation was affected by worksite preparedness planning, including the training and education of building occupants, and risk communication. The environmental conditions affecting evacuation included smoke, flames, debris, general condition and degree of crowdedness on staircases, and communication infrastructure systems (e.g., public address, landline, cellular and fire warden's telephones).

Conclusions:

Various factors at the individual, organizational, and environmental levels were identified that affected evacuation. Interventions that address the barriers to evacuation may improve the full-scale evacuation of other high-rise buildings under extreme conditions. Further studies should focus on the development and evaluation of targeted interventions, including model emergency preparedness planning for high-rise occupancies.
Prevalence and public health relevance of micronutrient deficiencies and undernutrition in pre-school children and women of reproductive age in Côte d'Ivoire, West Africa
Authors: Rohner Fabian , Northrop-Clewes Christine , Tschannen Andres B , Bosso Patrice E , Kouassi-Gohou Valérie , Erhardt Juergen G , Bui Mai , Zimmermann Michael B , Mascie-Taylor CG Nicholas
Published: September 2013

Objective

To provide nationally representative data on the prevalence of anaemia, vitamin A and Fe deficiencies among pre-school age children (pre-SAC) and non-pregnant women of reproductive age (WRA), and on vitamin B12and folate deficiencies in WRA, and the influence of inflammation on their interpretation.

Design

A cross-sectional survey to measure anthropometry, malaria parasitaemia and micronutrient status. Specifically, blood samples were analysed for Hb, plasma ferritin, soluble transferrin receptors, C-reactive protein, α1-acid glycoprotein, retinol-binding protein, vitamin B12and folate.

Setting

Côte d'Ivoire in 2007.

Subjects

Nine hundred and twenty-eight WRA and 879 pre-SAC.

Results

In WRA, prevalence ofPlasmodiumparasitaemia (5 %) was low, but inflammation (34 %) was higher. Anaemia was a severe public health problem and prevalence differed by residency and eco-region. Inflammation-adjusted Fe deficiency was highest in urban areas (20 %). Nationally, folate deficiency was 86 %, higher in urban areas and varied by eco-region. Prevalence of vitamin B12deficiency was low but higher in the rural areas and the north. Inflammation-adjusted vitamin A deficiency was very low (1 %). In pre-SAC, prevalence of inflammation (67 %) andPlasmodiumparasites (25 %) was high; the latter was associated with poverty, rural residency and higher ferritin concentrations. Anaemia was classified as a severe public health problem (72 %), and was higher in rural areas (76 %) and the north (87 %). A quarter of pre-SAC suffered from vitamin A deficiency (inflammation-adjusted) and prevalence of undernutrition was high.

Conclusions

Prevalence of inflammation,Plasmodiumparasitaemia and micronutrient deficiencies were high in Côte d'Ivoire, particularly in pre-SAC. Nutritional interventions should be accompanied by strategies to reduce exposure to infections.
Risk factors for childhood overweight: a 30-month longitudinal study of 3- to 6-year-old children
Authors: De Coen Valerie , De Bourdeaudhuij Ilse , Verbestel Vera , Maes Lea , Vereecken Carine
Published: September 2013

Objective

The increasing prevalence of childhood overweight is an important health issue. There is a need for longitudinal research among children in order to identify risk factors for childhood overweight. The objective of the present research was to identify potential sociodemographic and behavioural risk factors for development of childhood overweight among 3- to 6-year-old children.

Design

Longitudinal study.

Setting

Sixteen pre-primary and primary schools.

Subjects

BMI Z-scores at baseline and two follow-up measurements were calculated for 568 children. Sociodemographic, parental adiposity, familial composition, child's diet, physical activity and sedentary behavioural data were collected through questionnaires.

Results

Several risk factors for the development of childhood overweight were found. Being an only child, lower maternal educational level, maternal and paternal overweight, more than 1 h screen time on weekdays and high soft drinks consumption were shown to be positively associated with the development of childhood overweight.

Conclusions

Although behavioural factors are important, our findings support the thesis that interventions on the prevention of childhood overweight should focus on high-risk groups, i.e. children from low socio-economic background or with high parental BMI. Interventions should address the whole family and take into account their lifestyle and structure.
Judging Moral Issues in a Multicultural Society
Authors: Passini Stefano , Villano Paola
Published: September 2013

People’s reactions to crimes sometimes change depending on whether the perpetrators are members of their own ingroup or an outgroup. This observation results in questions concerning how moral reasoning works in intergroup situations. In this research, we analyzed the combined effect of the nationality of the protagonist in a moral dilemma and the participant’s social dominance orientation (SDO) attitudes on the participant’s level of moral reasoning. A total of 230 Italian participants responded to two moral dilemmas taken from the Defining Issues Test, which had been modified so that one was about an Italian and the other about a Romanian. The results showed a significant interaction between the dilemma, the protagonist’s nationality, and the participant’s SDO: The P scores (postconventional reasoning) of low-SDO participants were on the same level when they were judging people of either nationality, while high-SDO participants tended to have a higher P score when judging Italians as opposed to Romanians.
Modeling Individual Differences in Automatic Evaluation Measured by Evaluative Decision Task
Authors: Rebernjak Blaž , Buško Vesna
Published: September 2013

The study concerns the measurement of individual differences in the automatic processing of affective stimuli within an affective priming paradigm. Automatic processing measures, termed processing tendencies, were defined by parcels composed of difference score items of the Evaluative Decision Task reaction time variables. Confirmatory factor analytic framework was used (1) to construct parcels of individual items and to evaluate them in terms of unidimensionality and temporal invariance, (2) to examine the structure of relationships among the processing tendencies, and (3) to test the stability of individual differences in processing tendencies over a 4-week period. Random assignment of items to parcels showed unidimensionality as well as invariance over time. Processing tendencies relating to same-valence targets – facilitation and inhibition of positive targets as well as facilitation and inhibition of negative targets – showed a positive relationship at both timepoints not predicted by theory. Furthermore, evidence in favor of stability of individual differences in processing tendencies was obtained for positive targets, while the results for negative targets were less clear. The results are interpreted in light of current theories of automatic affective processing.
MOF-76: from a luminescent probe to highly efficient UVI sorption material
Authors: Yang Weiting , Bai Zhi-Qiang , Shi Wei-Qun , Yuan Li-Yong , Tian Tao , Chai Zhi-Fang , Wang Hao , Sun Zhong-Ming
Published: September 2013

MOF-76 exhibits not only high sensitivity for the detection of U(vi), but also high adsorption capacity of 298 mg g−1 at a low pH value of ∼3.0. Furthermore, the high selectivity for uranium adsorption over a series of competing metal ions is also illustrated.
Mycobacterium tuberculosis DNA gyrase ATPase domain structures suggest a dissociative mechanism that explains how ATP hydrolysis is coupled to domain motion
Authors: Agrawal Alka , Roué Mélanie , Spitzfaden Claus , Petrella Stéphanie , Aubry Alexandra , Hann Michael , Bax Benjamin , Mayer Claudine
Published: September 2013

DNA gyrase, a type II topoisomerase, regulates DNA topology by creating a double-stranded break in one DNA duplex and transporting another DNA duplex [T-DNA (transported DNA)] through this break. The ATPase domains dimerize, in the presence of ATP, to trap the T-DNA segment. Hydrolysis of only one of the two ATPs, and release of the resulting Pi, is ratelimiting in DNA strand passage. A long unresolved puzzle is how the non-hydrolysable ATP analogue AMP-PNP (adenosine 5′-[β,γ-imido]triphosphate) can catalyse one round of DNA strand passage without Pi release. In the present paper we discuss two crystal structures of the Mycobacterium tuberculosis DNA gyrase ATPase domain: one complexed with AMP-PCP (adenosine 5′-[β,γ-methylene]triphosphate) was unexpectedly monomeric, the other, an AMP-PNP complex, crystallized as a dimer. In the AMP-PNP structure, the unprotonated nitrogen (P-N=P imino) accepts hydrogen bonds from a well-ordered ‘ATP lid’, which is known to be required for dimerization. The equivalent CH2 group, in AMP-PCP, cannot accept hydrogen bonds, leaving the ‘ATP lid’ region disordered. Further analysis suggested that AMP-PNP can be converted from the imino (P-N=P) form into the imido form (P-NH-P) during the catalytic cycle. A main-chain NH is proposed to move to either protonate AMP-P-N=P to AMP-P-NH-P, or to protonate ATP to initiate ATP hydrolysis. This suggests a novel dissociative mechanism for ATP hydrolysis that could be applicable not only to GHKL phosphotransferases, but also to unrelated ATPases and GTPases such as Ras. On the basis of the domain orientation in our AMP-PCP structure we propose a mechanochemical scheme to explain how ATP hydrolysis is coupled to domain motion.
Analysis of transmit antenna selection with output‐threshold generalised selection combining over Rayleigh fading
Authors: Tan Beng Soon , Li Kwok Hung , Teh Kah Chan
Published: September 2013

In this study, the authors propose a diversity‐combining scheme with transmit antenna selection (TAS) and output‐threshold generalised selection combining (OT‐GSC) receiver. It is shown that the proposed TAS/OT‐GSC can achieve similar performance as compared to the TAS/GSC with a reduced number of channel estimates when the predetermined signal‐to‐noise ratio (SNR) threshold is optimised. The outage probability, average output SNR, and symbol‐error rate (SER) expressions of the proposed TAS/OT‐GSC scheme are derived and presented over independent and non‐identically distributed Rayleigh‐fading channels. The analytical expressions are validated by simulation results. The trade‐off comparisons in terms of the SER and number of channel estimates between the TAS/OT‐GSC and TAS/GSC are discussed. Lastly, the capacity between the TAS/OT‐GSC and TAS/GSC is compared.
Performance of multiband orthogonal frequency division multiplexing network in ultra wideband channels incorporating people shadowing and channel fading
Authors: Bhaskar Vidhyacharan , Devi Panneerselvam Anita
Published: September 2013

Ultra wideband (UWB) systems transmit signals across a much wider frequency than conventional systems and are usually very difficult to detect. UWB systems tend to be useful for short‐range indoor applications. However, because of the short duration of UWB pulses, it is easier to engineer extremely high data rates. In multi‐band orthogonal frequency division multiplexing (MB‐OFDM) architecture, designers gain flexibility, reduction in power consumption, high spectrum efficiency and cost. In the earlier study, people shadowing has been considered to model attenuation in a packet‐level UWB channel model. However, in dense short‐range indoor applications, the effect of scatterers, diffractors and reflectors cannot be ignored. This happens mostly when the transmit antenna is omni‐directional. Compared with the earlier work which incorporated only shadowing effects, this study discusses a packet‐level UWB channel model subject to both multipath fading and people shadowing, which can arise even in an indoor channel (e.g. inside a hall of dimensions ∼ 10 m), and is incorporated in an MB‐OFDM system. The performance analysis of the link is made based on link throughput and delay in servicing packets. The numerical results show the relative effects of various fading distributions, viz., Rayleigh, Rician, Weibull and Nakagami, together with people shadowing on the MB‐OFDM system.
Error performance analysis of decode‐and‐forward and amplify‐and‐forward multi‐way relay networks with binary phase shift keying modulation
Authors: Islam Shama Naz , Sadeghi Parastoo , Durrani Salman
Published: September 2013

In this study, we analyse the error performance of decode and forward (DF) and amplify and forward (AF) multi‐way relay networks (MWRNs). The authors consider a MWRN with pair‐wise data exchange protocol using binary phase shift keying (BPSK) modulation in both additive white Gaussian noise (AWGN) and Rayleigh fading channels. The authors quantify the possible error events in an L‐user DF or AF MWRN and derive accurate asymptotic bounds on the probability for the general case that a user incorrectly decodes the messages of exactly k (k ∈ [1, L − 1]) users. They show that at high signal‐to‐noise ratio (SNR), the higher order error events (k ≥ 3) are less probable in AF MWRN, but all error events are equally probable in a DF MWRN. They derive the average BER of a user in a DF or AF MWRN in both AWGN and Rayleigh fading channels under high SNR conditions. Simulation results validate the correctness of the derived expressions. The authors results show that at medium to high SNR, DF MWRN provides better error performance than AF MWRN in AWGN channels even with a large number of users (e.g. L = 100). Whereas, AF MWRN outperforms DF MWRN in Rayleigh fading channels even for much smaller number of users (e.g. L > 10).
Distributed consensus protocols for coordinated control of multiple quadrotors under a directed topology
Authors: Wang Yinqiu , Wu Qinghe , Wang Yao
Published: September 2013

Two distributed consensus problems, including leadless consensus and tracking consensus, for multiple quadrotors with bounded disturbances under a directed topology are solved in this study. First, the model of a single quadrotor is divided into two subsystems. Some coupling terms between the two subsystems are regarded as external perturbations. For the case of leadless consensus, a distributed sliding‐mode controller for the first subsystem and a state‐feedback controller for the second subsystem are proposed to guarantee that the consensus is achieved with bounded errors that are only associated with disturbances. For the case of tracking consensus, by using the proposed sliding‐mode consensus protocols combining with two sliding‐mode observers, it is shown that all quadrotors can track the leader with bounded errors which can be manipulated suitably. Simulations show the effectiveness of the proposed control protocols.
Observation of Frenkel and charge transfer excitons in pentacene single crystals using spectroscopic generalized ellipsometry
Authors: Qi Dongchen , Su Haibin , Bastjan M. , Jurchescu O. D. , Palstra T. M. , Wee Andrew T. S. , Rübhausen M. , Rusydi A.
Published: September 2013

We report on the emerging and admixture of Frenkel and charge transfer (CT) excitons near the absorption onset in pentacene single crystals. Using high energy-resolution spectroscopic generalized ellipsometry with in-plane polarization dependence, the excitonic nature of three lowest lying excitations is discussed. Their distinct polarization dependence strongly indicates the presence of both Frenkel and CT types of excitons near the excitation onset. In particular, the peculiar polarization behavior of the second excitation can only be rationalized by taking into account the inherent CT transition dipole moment. This observation has important implications for the pentacene-based optoelectronic devices.
Modified poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) source/drain electrodes for fully printed organic field-effect transistors consisting of a semiconductor blend
Authors: Schmidt G. C. , Höft D. , Bhuie M. , Haase K. , Bellmann M. , Haidu F. , Lehmann D. , Zahn D. R. T. , Hübler A. C.
Published: September 2013

The influence of post-press treatment on the modification of printed source/drain electrodes made of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with ethylene glycol is presented. Beside changes of the geometry and the conductivity of these mass printed structures, the work function of PEDOT:PSS can be tuned, leading to an improved performance of organic field effect transistors (OFETs). OFETs were built up with a new small molecule/polymer blend consisting of 6,13-bis[(cyclopropyldiisopropylsilyl)ethynyl] pentacene and poly(triarylamine), providing a field effect mobility of 0.2 cm2/Vs for fully printed devices in air. Ring oscillators based on these OFETs demonstrate a frequency of more than 1 kHz.
Biomass pyrolysis: Thermal decomposition mechanisms of furfural and benzaldehyde
Authors: Vasiliou AnGayle K. , Kim Jong Hyun , Ormond Thomas K. , Piech Krzysztof M. , Urness Kimberly N. , Scheer Adam M. , Robichaud David J. , Mukarakate Calvin , Nimlos Mark R. , Daily John W. , Guan Qi , Carstensen Hans-Heinrich , Ellison G. Barney
Published: September 2013

The thermal decompositions of furfural and benzaldehyde have been studied in a heated microtubular flow reactor. The pyrolysis experiments were carried out by passing a dilute mixture of the aromatic aldehydes (roughly 0.1%–1%) entrained in a stream of buffer gas (either He or Ar) through a pulsed, heated SiC reactor that is 2–3 cm long and 1 mm in diameter. Typical pressures in the reactor are 75–150 Torr with the SiC tube wall temperature in the range of 1200–1800 K. Characteristic residence times in the reactor are 100–200 μsec after which the gas mixture emerges as a skimmed molecular beam at a pressure of approximately 10 μTorr. Products were detected using matrix infrared absorption spectroscopy, 118.2 nm (10.487 eV) photoionization mass spectroscopy and resonance enhanced multiphoton ionization. The initial steps in the thermal decomposition of furfural and benzaldehyde have been identified. Furfural undergoes unimolecular decomposition to furan + CO: C4H3O–CHO (+ M) → CO + C4H4O. Sequential decomposition of furan leads to the production of HC≡CH, CH2CO, CH3C≡CH, CO, HCCCH2, and H atoms. In contrast, benzaldehyde resists decomposition until higher temperatures when it fragments to phenyl radical plus H atoms and CO: C6H5CHO (+ M) → C6H5CO + H → C6H5 + CO + H. The H atoms trigger a chain reaction by attacking C6H5CHO: H + C6H5CHO → [C6H6CHO]* → C6H6 + CO + H. The net result is the decomposition of benzaldehyde to produce benzene and CO.
Three-dimensional Lagrangian transport phenomena in unsteady laminar flows driven by a rotating sphere
Authors: Moharana N. R. , Speetjens M. F. M. , Trieling R. R. , Clercx H. J. H.
Published: September 2013

Magnetic actuation of microscopic beads is a promising technique for enhancement and manipulation of scalar transport in micro-fluidic systems. This implies laminar and essentially three-dimensional (3D) unsteady flow conditions. The present study addresses fundamental transport phenomena in such configurations in terms of 3D coherent structures formed by the Lagrangian fluid trajectories in a 3D time-periodic flow driven by a rotating sphere. The flow field is represented by an exact Stokes solution superimposed by a nonlinear closed-form perturbation. This facilitates systematic “activation” and exploration of two fundamental states: (i) invariant spheroidal surfaces accommodating essentially 2D Hamiltonian dynamics; (ii) formation of intricate 3D coherent structures (spheroidal shells interconnected by tubes) and onset to 3D dynamics upon weak perturbation of the former state. Key to the latter state is emergence of isolated periodic points and the particular foliation and interaction of the associated manifolds, which relates intimately to coherent structures of the unperturbed state. The occurrence of such fundamental states and corresponding dynamics is (qualitative) similar to findings on a realistic 3D lid-driven flow subject to weak fluid inertia. This implies, first, a universal response scenario to weak perturbations and, second, an adequate representation of physical effects by the in essence artificial perturbation. The study thus offers important new insights into a class of flow configurations with great practical potential.
Dissipative particle dynamics study of translational diffusion of rigid-chain rodlike polymer in nematic phase
Authors: Zhao Tongyang , Wang Xiaogong
Published: September 2013

In this study, dissipative particle dynamics (DPD) method was employed to investigate the translational diffusion of rodlike polymer in its nematic phase. The polymer chain was modeled by a rigid rod composed of consecutive DPD particles and solvent was represented by independent DPD particles. To fully understand the translational motion of the rods in the anisotropic phase, four diffusion coefficients, $D_{||}^{\bf u}$D‖u, $D_ \bot ^{\bf u}$D⊥u, $D_{||}^{\bf n}$D‖n, $D_ \bot ^{\bf n}$D⊥n were obtained from the DPD simulation. By definition, $D_{||}^{\bf n}$D‖n and $D_ \bot ^{\bf n}$D⊥n denote the diffusion coefficients parallel and perpendicular to the nematic director, while $D_{||}^{\bf u}$D‖u and $D_ \bot ^{\bf u}$D⊥u denote the diffusion coefficients parallel and perpendicular to the long axis of a rigid rod u. In the simulation, the velocity auto-correlation functions were used to calculate the corresponding diffusion coefficients from the simulated velocity of the rods. Simulation results show that the variation of orientational order caused by concentration and temperature changes has substantial influences on $D_{||}^{\bf u}$D‖u and $D_ \bot ^{\bf u}$D⊥u. In the nematic phase, the changes of concentration and temperature will result in a change of local environment of rods, which directly influence $D_{||}^{\bf u}$D‖u and $D_ \bot ^{\bf u}$D⊥u. Both $D_{||}^{\bf n}$D‖n and $D_ \bot ^{\bf n}$D⊥n can be represented as averages of $D_{||}^{\bf u}$D‖u and $D_ \bot ^{\bf u}$D⊥u, and the weighted factors are functions of the orientational order parameter S2. The effect of concentration and temperature on $D_{||}^{\bf n}$D‖n and $D_ \bot ^{\bf n}$D⊥n demonstrated by the DPD simulation can be rationally interpreted by considering their influences on $D_{||}^{\bf u}$D‖u, $D_ \bot ^{\bf u}$D⊥u and the order parameter S2.
Bi-stability in the turbulent wake past parallelepiped bodies with various aspect ratios and wall effects
Authors: Grandemange M. , Gohlke M. , Cadot O.
Published: September 2013

The turbulent wake past parallelepiped bodies with a rectangular blunt trailing edge of height H and width W is investigated in wall proximity: various aspect ratios H* = H/W ∈ [0.51, 1.63] and ground clearances C* = C/W ∈ [0, 1.00] are explored at a Reynolds number of 4.5 × 104 based on the body width W. Base pressure measurements and particle image velocimetry show that the close wake often undergoes antisymmetric instabilities that can be either in the lateral direction (parallel to the wall) or in the vertical direction (normal to the wall). The instantaneous wake presents preferred states with high degrees of asymmetry; in some configurations, topology shifts are observed after long time scales Tl ∼ 103W/U0 leading to bistable behaviors. The effect of ground proximity is thoroughly studied for H* = 0.74 corresponding to the reference Ahmed geometry and for a case with a height dimension larger than its width H* = 1/0.74 = 1.34. When C* > 0.08, it is found that the Ahmed body is bistable in the lateral direction while the wake past the second geometry develops an instability in the vertical direction. In both cases, the instabilities vanish for sufficiently small values of ground clearance (C* < 0.08) which are associated with the apparition of a detachment of the underbody flow on the ground. However, the wall proximity does not necessarily stabilize the wake in the plane of symmetry since the flow retrieves the bi-stability in the lateral direction for C* < 0.03 and H* < 0.65. A general criterion for the existence of the instabilities is deduced from the parametric study in the domain (H*, C*) together with symmetry considerations.
Compensation doping in InGaAs / GaAsP multiple quantum well solar cells for efficient carrier transport and improved cell performance
Authors: Fujii Hiromasa , Wang Yunpeng , Watanabe Kentaroh , Sugiyama Masakazu , Nakano Yoshiaki
Published: September 2013

A major challenge for multiple quantum well (MQW) solar cells is to extract sufficient photo-excited carriers to an external circuit through the MQW region under forward bias. The present study reports the effectiveness of compensation doping in the i-region, which includes MQWs, for more efficient transport of both electrons and holes. Unintentional p-type background doping occurs in GaAs by inevitable carbon incorporation during metal-organic vapor phase epitaxy, causing undesirable bending of the band lineup in the i-region of p-on-n devices. By cancelling this out by sulfur compensation doping to obtain a uniform electric field distribution, we achieved much a high carrier collection efficiency (CCE) >90% at the operating bias voltage regardless of the excitation wavelength, compared to < 50% without compensation doping. Consequently, cell performance was greatly improved, in particular showing an enhancement of the fill factor from 0.54 to 0.77, and degradation-free quantum efficiency within the GaAs absorption wavelength range. The photoluminescence (PL) intensity from the MQW increased as the CCE decreased at a large forward bias, and radiative recombination loss was significantly suppressed by compensation doping. Furthermore, time-resolved PL measurements indicated a much higher speed of carrier escape from the wells, showing a quicker PL decay time of 7 ns at 0.6 V, compared to 18–51 ns without compensation doping.
The effect of silicon doping in the barrier on the electroluminescence of InGaN/GaN multiple quantum well light emitting diodes
Authors: Wu Xiaoming , Liu Junlin , Xiong Chuanbing , Zhang Jianli , Quan Zhijue , Mao Qinghua , Jiang Fengyi
Published: September 2013

InGaN/GaN multiple quantum well (MQW) light emitting diodes were grown on silicon substrate by metal organic chemical vapor deposition. A different barrier was heavily doped with silicon based on the same structure. Temperature dependent electroluminescence was performed on the devices. The results reveal that heavily doping the barrier distant from the n-type layer with silicon causes two emission peaks. As the doped barrier gets closer to n-type layer, the energy gap between the two peaks becomes narrower. Silicon doped in the barrier is believed to generate p-n junction built-in field from the doped barrier towards p-type layer. This field compensates the piezoelectric field in the well(s) between the doped barrier and p-type layer. It results in higher emission energy of this (these) well(s). When the doped barrier gets closer to the n-type layer, the compensation is less significant.
Observation of exclusively π-stacked heterodimer of indole and hexafluorobenzene in the gas phase
Authors: Kumar Sumit , Das Aloke
Published: September 2013

In this study, the structure of the indole · · · hexafluorobenzene dimer has been investigated in the gas phase by using resonant two photon ionzation (R2PI) and IR-UV double resonance spectroscopy combined with quantum chemistry calculations. We have confirmed the presence of exclusively π-stacked structure of the dimer from both experimental and theoretical IR spectra in the N–H stretching region. Observation of a single stable structure of the dimer has also been verified through 3D potential energy surface scan of the π-stacked dimer by varying the parallel displacement of the hexafluorobenzene unit simultaneously along the major and minor axes of the indole moiety. π-stacking interaction is present very often between the tryptophan and phenylalanine residues in proteins. But this interaction has not been observed earlier in the gas phase experiment by studying indole · · · benzene dimer because the N–H group of indole predominately directs towards the N–H · · · π hydrogen bonded T-shaped structure. The chosen molecular systems in this study not only rule out the possibility of the formation of the N–H · · · π bound T-shaped dimer but also enable the determination of the structure by probing the N–H group. The π-stacked indole · · · hexafluorobenzene dimer has a unique structure where the center of the hexafluorobenznene ring is aligned with the center of the shared bond of the indole ring. Our work provides useful insight in designing unnatural proteins having strong π-stacking interaction between the tryptophan and phenylalanine residues.
Non-diffusive relaxation of a transient thermal grating analyzed with the Boltzmann transport equation
Authors: Collins Kimberlee C. , Maznev Alexei A. , Tian Zhiting , Esfarjani Keivan , Nelson Keith A. , Chen Gang
Published: September 2013

The relaxation of an one-dimensional transient thermal grating (TTG) in a medium with phonon-mediated thermal transport is analyzed within the framework of the Boltzmann transport equation (BTE), with the goal of extracting phonon mean free path (MFP) information from TTG measurements of non-diffusive phonon transport. Both gray-medium (constant MFP) and spectrally dependent MFP models are considered. In the gray-medium approximation, an analytical solution is derived. For large TTG periods compared to the MFP, the model yields an exponential decay of grating amplitude with time in agreement with Fourier's heat diffusion equation, and at shorter periods, phonon transport transitions to the ballistic regime, with the decay becoming strongly non-exponential. Spectral solutions are obtained for Si and PbSe at 300 K using phonon dispersion and lifetime data from density functional theory calculations. The spectral decay behaviors are compared to several approximate models: a single MFP solution, a frequency-integrated gray-medium model, and a “two-fluid” BTE solution. We investigate the utility of using the approximate models for the reconstruction of phonon MFP distributions from non-diffusive TTG measurements.
Mach-Zehnder refractometric sensor using long-range surface plasmon waveguides
Authors: Khan Asad , Krupin Oleksiy , Lisicka-Skrzek Ewa , Berini Pierre
Published: September 2013

We demonstrate refractometric sensing using long-range surface plasmons on a compact integrated Mach-Zehnder interferometer (MZI) formed from thin Au stripes in Cytop with an etched microfluidic channel defining the sensing arm. The transfer characteristics of MZIs were obtained by sequentially injecting solutions of increasing refractive index in the sensing arm. A detection limit of 9 × 10−7 RIU was achieved at λ0 = 1310 nm, limited by unbalanced losses in the sensing and reference arms. A model is proposed for the MZIs, taking into account all loss mechanisms, and may be applied to MZI sensors in other technologies.
Supercontinuum generation in water doped with gold nanoparticles
Authors: Vasa Parinda , Singh Mamraj , Bernard Rodney , Dharmadhikari Aditya K. , Dharmadhikari Jayashree A. , Mathur Deepak
Published: September 2013

We report enhanced supercontinuum generation in water doped with gold nanoparticles of different shapes under modest ultrafast (35 fs) laser excitation. Reasonably, flat supercontinuum spectra covering ∼1.45–2 eV (855–620 nm) are observed with as much as ∼161 meV (63 nm) increase in the visible extent compared to pure water for dopants whose surface plasmon resonance (SPR) overlaps the excitation laser spectrum. We use a phenomenological self-phase modulation model to rationalize our results, taking cognizance of plasma contributions to the third-order susceptibility of water along with SPR-induced field enhancement. Such large spectral broadening may be useful for several applications involving imaging or microscopy with modest incident intensities.
Study of the effect of the stress on CdTe nuclear detectors
Authors: Ayoub M. , Hage-Ali M. , Radley I. , Mullins J. T.
Published: September 2013

CdTe detectors are commonly used for X and γ ray applications. The performance of these detectors is strongly affected by different types of mechanical stress; such as that caused by differential expansion between the semiconductor and its intimate metallic contacts and that caused by applied pressure during the bonding process. The aim of this work was to study the effects of stress on the performance of CdTe detectors. A difference in expansion coefficients induces transverse stress under the metallic contact, while contact pressure induces longitudinal stress. These stresses have been simulated by applying known static pressures. For the longitudinal case, the pressure was applied directly to the metallic contact; while in the transverse case, it was applied to the side. We have studied the effect of longitudinal and transverse stresses on the electrical characteristics including leakage current measurements and γ-ray detection performance. We have also investigated induced defects, their nature, activation energies, cross sections, and concentrations under the applied stress by using photo-induced current transient spectroscopy and thermoelectric effect spectroscopy techniques. The operational stress limit is also given.