bluuebunny/crossref_metadata_2025 huggingface dataset:
College chemistry students' mental models of acids and acid strength
Authors: McClary LaKeisha , Talanquer Vicente
Published: January 2011

The central goal of this study was to characterize the mental models of acids and acid strength expressed by advanced college chemistry students when engaged in prediction, explanation, and justification tasks that asked them to rank chemical compounds based on their relative acid strength. For that purpose we completed a qualitative research study involving students enrolled in different types of organic chemistry course sections at our university. Our analysis led to the identification of four distinct mental models, some of which resembled scientific models of acids and acid strength. However, the distinct models are better characterized as synthetic models that combined assumptions from one or more scientific models with intuitive beliefs about factors that determine the properties of chemical substances. For many students in our sample, mental models served more as tools for heuristic decision‐making based on intuitively appealing, but many times mistaken, concept associations rather than as cognitive tools to generate explanations. Although many research participants used a single general mental model to complete all of the interview tasks, the presence of specific problem features or changes in the nature of the task (e.g., prediction vs. explanation) prompted several students to change their mental model or to add a different mental representation. Our study indicates that properly diversifying and sequencing the types of academic tasks in which students are asked to participate could better foster meaningful learning as different types of cognitive resources may be activated by different students, and thus shared, analyzed, and discussed. © 2011 Wiley Periodicals, Inc., Inc. J Res Sci Teach 48: 396–413, 2011
Study of a wireless multimodal sensing system integrated with an electrical conductivity sensor and a temperature sensor for the health control of cows
Authors: Futagawa Masato , Ishida Mitsuyoshi , Ishida Makoto , Sawada Kazuaki
Published: January 2011

Improved technology for the real‐time, continuous monitoring of health of the animals is an important requirement for the animal production industry. We have studied a multimodal sensor consisting of integrated electrical conductivity (EC) and temperature sensors, a wireless unit, and some circuit boards. We measured the information relayed by the integrated sensor located at several positions within the first stomach (known as ‘the rumen’) in cows. The wireless unit was able to simultaneously monitor the EC and temperature sensors. The results of these tests showed that the developed unit is a useful tool, since the data obtained were reasonable. We then measured the RF field strength as a function of the distance between the wireless unit and the antenna. We calculated the performance that is required in terms of the received power to accurately transmit results from the rumen. We confirmed that the unit could achieve the necessary performance to send data from the rumen to the receiver. We could also find a criterion for the amount of RF power necessary for successful measurements from rumen. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Performance of DS‐UWB in MB‐OFDM and multi‐user interference over Nakagami‐mfading channels
Authors: Mehbodniya Abolfazl , Aïssa Sonia
Published: January 2011

The mutual interference between the two ultra wideband (UWB) technologies, which use the same frequency spectrum, will be a matter of concern in the near future. In this context, we present a performance analysis of direct‐sequence (DS) UWB communication in the presence of multiband orthogonal frequency division multiplexing (MB‐OFDM) UWB interfering transmissions. The channel fading is modeled according to Nakagami‐m distribution, and multi‐user interference is taken into account. The DS‐UWB system performance is evaluated in terms of bit error rate (BER). Specifically, using the characteristic function approach, an analytical expression for the average BER is derived conditioned on the channel impulse response. Numerical and simulation results are provided and compared for different coexistence scenarios. Copyright © 2011 John Wiley & Sons, Ltd.
Pre‐filtering technique for MAI cancellation in MC‐CDMA systems
Authors: Chang Tain‐Sao , Yen Cherng‐Chang , Yang Ya‐Yin , Wen Jyh‐Horng
Published: January 2011

Multicarrier code division multiple access (MC‐CDMA), is a promising multiplexing technique for future communication systems. In this study, we employ the well‐known Walsh‐Hadamard spreading codes for synchronous downlink transmission of MC‐CDMA systems. The spreading codes allow that the frequency diversity to be efficiently exploited. However, multipath propagation may cause orthogonality among users is distorted, and this distortion produces multiple access interference (MAI). To eliminate this effect, we propose a pre‐filtering‐based MC‐CDMA system which uses a pre‐filtering technique at the transmitter and an equal gain combining (EGC) scheme at the receivers, respectively. Our proposed pre‐filtering technique transforms the transmitted signals so that the MAI can be eliminated, and the EGC scheme weights the signals received from all subcarriers so that channel distortions can be compensated. Furthermore, the proposed technique can calculate the transmitted power over all subcarriers to satisfy the required quality of service of each user and archive MAI‐free. In this paper, performance in terms of bit error rate is analyzed; in comparison with the EGC, orthogonal restoring combining, and maximal ratio combining schemes at receiver, respectively. Copyright © 2011 John Wiley & Sons, Ltd.
Connecting Youth Violence Prevention, Positive Youth Development, and Community Mobilization
Authors: Allison Kevin W. , Edmonds Torey , Wilson Karen , Pope Michell , Farrell Albert D.
Published: January 2011

Several disconnects serve to weaken the use of evidence based programming in community settings. Communities face the need to address the challenges of multiple risk behaviors faced by adolescents in their communities, but must also work to support successful transitions to adulthood and the broader positive development of their youth. The stronger integration of positive youth development and prevention of youth risk at the community level may offer an opportunity to support the implementation and ongoing development of evidence‐based practices (EBPs). This article provides an overview of the VCU Clark‐Hill Institute for Positive Youth Development Institute's community mobilization effort in Richmond, Virginia and reports preliminary findings from our integrated mobilization efforts. First, we review the role of our Community Advisory Council in their collaborative work to support positive youth development and reduce risk for youth violence. Next, we present examples of institute efforts in providing technical assistance relevant to supporting the use and development of EBPs. We then discuss the adaptation of an evidence‐based program to target positive youth development. We also present overviews from qualitative investigations examining barriers and supports that inform and are relevant to the implementation of EBPs. Finally, we consider ways in which community efforts inform and shape institute efforts to develop EPBs. Taken together, these activities provide examples of how community‐based mobilization efforts can integrate and inform the implementation of EBPs and the role and use of prevention science as a tool in supporting effective programming to promote positive youth development and prevent youth violence.
Dual- and multi-energy CT: approach to functional imaging
Authors: Fornaro Juergen , Leschka Sebastian , Hibbeln Dennis , Butler Anthony , Anderson Nigel , Pache Gregor , Scheffel Hans , Wildermuth Simon , Alkadhi Hatem , Stolzmann Paul
Published: January 2011

The energy spectrum of X-ray photons after passage through an absorber contains information about its elemental composition. Thus, tissue characterisation becomes feasible provided that absorption characteristics can be measured or differentiated. Dual-energy CT uses two X-ray spectra enabling material differentiation by analysing material-dependent photo-electric and Compton effects. Elemental concentrations can thereby be determined using three-material decomposition algorithms. In comparison to dual-energy CT used in clinical practice, recently developed energy-sensitive photon-counting detectors sample the material-specific attenuation curves at multiple energy levels and within narrow energy bands; the latter allows the detection of element-specific, k-edge discontinuities of the photo-electric cross section. Multi-energy CT imaging therefore is able to concurrently identify multiple materials with increased accuracy. These specific data on material distribution provide information beyond morphological CT, and approach functional imaging. This article reviews the principles of dual- and multi-energy CT imaging, hardware approaches and clinical applications.
Urodynamic and clinical effects of transvaginal mesh repair for severe cystocele with and without urinary incontinence
Authors: Liang Ching‐Chung , Lin Yi‐Hao , Chang Yao‐Lung , Chang Shuenn‐Dhy
Published: January 2011

Objective

To demonstrate the urodynamic and clinical effects of transvaginal polypropylene mesh repair (TVM) for severe cystocele with or without stress urinary incontinence (SUI).

Methods

One hundred women with severe cystocele who underwent transvaginal cystocele repair using a tension‐free polypropylene mesh were included in a retrospective study. A simultaneous transobturator tape (TOT) procedure was performed in 24 patients with concurrent urodynamic stress incontinence (USI). Postoperative follow‐up examinations included urodynamic testing, pelvic organ prolapse quantification, and urogynecologic questionnaire.

Results

Mean follow‐up was 35 months (range, 13–68 months). At 3–6 months after surgery, 2 (8.3%) of the 24 patients with USI who had undergone TVM and TOT had persistent SUI. Of the 30 women with occult USI who had undergone TVM alone, 6 (20%) developed symptomatic SUI and 9 (30%) had asymptomatic SUI. Thirteen (28.3%) of the 46 patients without USI developed postoperative SUI. The 1‐year results showed de novo SUI in 10 (10%) women, recurrent cystocele in 6 (6%), and mesh erosions in 5 (5%). Four (13.3%) of the 30 patients engaging in sexual activity had dyspareunia.

Conclusion

TVM is effective and safe in patients with severe cystocele, but may have an impact on voiding and sexual activity.
Polycystic ovary syndrome and increased polyp numbers as risk factors for malignant transformation of endometrial polyps in premenopausal women
Authors: Kilicdag Esra B. , Haydardedeoglu Bulent , Cok Tayfun , Parlakgumus Ayse H. , Simsek Erhan , Bolat Filiz A.
Published: January 2011

Objective

To determine the pre‐malignant and malignant potential of endometrial polyps and to assess whether different clinical parameters are associated with malignancy in the polyps of premenopausal women.

Methods

The clinical records of operative office hysteroscopic and resectoscopic procedures for endometrial polyps in 417 premenopausal women who attended Baskent University were examined over a retrospective period of 30 months. Only premenopausal patients were included in the study.

Results

In 97.8% of women, histology showed benign endometrial pathology. In 2.2% of women, pre‐malignant or malignant conditions were found in the polyp. Polycystic ovary syndrome (PCOS) and the presence of 2 or more polyps were associated with significant pre‐malignant or malignant changes.

Conclusion

The presence of irregular vaginal bleeding was not a predictor of malignancy in the polyp. Premenopausal women with PCOS and those with 2 or more polyps had an increased prevalence of polyp malignancy. These groups of patients, whether symptomatic or not, should be evaluated by hysteroscopic resection of the polyps.
The concept of cryo-conditioning in landscape evolution
Authors: Berthling Ivar , Etzelmüller Bernd
Published: January 2011

Recent accounts suggest that periglacial processes are unimportant for large-scale landscape evolution and that true large-scale periglacial landscapes are rare or non-existent. The lack of a large-scale topographical fingerprint due to periglacial processes may be considered of little relevance, as linear process–landscape development relationships rarely can be substantiated. Instead, periglacial landscapes may be classified in terms of specific landform associations. We propose “cryo-conditioning”, defined asthe interaction of cryotic surface and subsurface thermal regimes and geomorphic processes, as an overarching concept linking landform and landscape evolution in cold regions. By focusing on the controls on processes, this concept circumvents scaling problems in interpreting long-term landscape evolution derived from short-term processes. It also contributes to an unambiguous conceptualization of periglacial geomorphology. We propose that the development of several key elements in the Norwegian geomorphic landscape can be explained in terms of cryo-conditioning.
Evolutionary diversification of bruchine beetles: climate-dependent traits and development associated with pest status
Authors: Tuda M.
Published: January 2011

A number of insect species infest human households and stored foods and products, leading to their designation as pests. Until recently, little was known about the factors driving the evolution of pests that feed on stored dry foods. Here, I review the effects of changes in climate and species interactions on the evolution and ecology of beetles that feed on dried seeds/grains. My review focuses on evidence that the host utilization by part of the species in the subfamily Bruchinae (Chrysomelidae) is a preadaptation for utilizing stored dry seeds and grains, thus leading to their status as a pest. These and other stored product pest beetles retain a higher percentage of water in their body, relative to the water content of their diet, than beetles that feed on fresh crops. I review the studies that have documented adaptation, acclimation and polyphenetic response to high temperatures and desiccation and/or made direct comparisons between these traits between developmental stages, populations and among higher taxonomic groups. Finally, I review evidence for the effects of environmental change on insect host-parasitoid and competitor assemblages.
Developing a carer communication intervention to support personhood and quality of life in dementia
Authors: YOUNG TONY JOHNSTONE , MANTHORP CHRIS , HOWELLS DAVID , TULLO ELLEN
Published: January 2011

Dementia and dementia care present huge and growing challenges, both to individuals and to societies worldwide. In the United Kingdom, the context for the study reported here, recent key policy initiatives have highlighted problems in care provision, noting a lack of appropriate carer guidance, and an overemphasis on strictly biomedical interventions. Communication practices which support agency and empowerment have been identified as areas for particular improvement. A number of communication training and guidance packages are currently available, but these exhibit shortcomings, including a lack of user input and cross-referencing to other communications theory or to relevant empirical evidence; a lack of individualisation; and high context-specificity. In general, their uptake and level of application to care is very low. As a response, the study described here developed a new communications intervention characterised by the direct involvement of a broad spectrum of lay and professional stakeholders. This inter-group dialogue produced an agreed free-to-users, user-informed and user-relevant dementia communications toolkit (DEMTEC), which is empirically supported and adaptable to different socio-cultural and care environments. We detail the conceptual background to the toolkit, the inclusive and iterative methodology for its formulation, and how it can be used to help support ‘personhood’ and quality of life and to challenge the socially-constructed ‘othering’ of people with dementia.
WHAT IS MONEY? AN ALTERNATIVE TO SEARLE'S INSTITUTIONAL FACTS
Authors: Smit J. P. , Buekens Filip , du Plessis Stan
Published: January 2011

In The Construction of Social Reality (1995), John Searle develops a theory of institutional facts and objects, of which money, borders and property are presented as prime examples. These objects are the result of us collectively intending certain natural objects to have a certain status, i.e. to ‘count as’ being certain social objects. This view renders such objects irreducible to natural objects. In this paper we propose a radically different approach that is more compatible with standard economic theory. We claim that such institutional objects can be fully understood in terms of actions and incentives, and hence the Searlean apparatus solves a non-existent problem.
THE INCIDENTAL ACQUISITION OF ENGLISH PLURAL –S BY JAPANESE CHILDREN IN COMPREHENSION-BASED AND PRODUCTION-BASED LESSONS
Authors: Shintani Natsuko , Ellis Rod
Published: January 2011

Most studies that have investigated the effects of instruction on the SLA of specific grammatical features have focused on intentional learning. This study investigated incidental acquisition by comparing the relative effects of two types of instruction—comprehension-based instruction (CBI) and production-based instruction (PBI)—on young Japanese learners’ incidental acquisition of English plural –s. Results showed that both the CBI and PBI groups performed significantly better than the control group on both the comprehension and production tests. There were no statistically significant differences between the two experimental groups. However, a comparison of those learners in the two groups who were complete beginners indicated an advantage for the CBI instruction. A quantitative and qualitative analysis of the interactions in one CBI and one PBI class showed that the students who received both kinds of instruction had ample exposure to plural –s nouns but that the nature of the corrective feedback they received differed. Whereas the feedback that the students in the CBI group received on their comprehension errors enabled them to distinguish the meanings of plural and singular nouns, the feedback that the students in the PBI group received on their production errors—in the form of recasts—did not result in the repair of errors.
Transmission of swine pathogens: different means, different needs
Authors: Desrosiers Robert
Published: January 2011

There seems to be two main types of pathogens that cause diseases in swine: those that are mainly introduced through direct pig contacts, and those that are often, and in some situations mainly introduced by indirect transmission means. In this review, the mange mite (Sarcoptes scabiei), toxigenicPasteurella multocidaandBrachyspira hyodysenteriaewill be used as examples of the first type, and foot and mouth disease virus,Mycoplasma hyopneumoniaeand porcine reproductive and respiratory syndrome (PRRS) virus as examples of the second. It is now clear from various epidemiological studies as well as experimental and field data that aerosol transmission of some swine pathogens plays an important role in their epidemiology. As previous biosecurity programs did not take this factor into consideration, it can at least partially explain why many of these programs suffered frequent failures and why air filtration is now becoming increasingly popular in North America. Identifying and quantifying transmission means should be a priority for every important infectious disease for which it has not been done.
Writing African American Migrations
Authors: Blocker Jack S.
Published: January 2011

Efforts to write the history of the African American migrations of the Civil War era, the Gilded Age, and the Progressive Era began soon after the start of these historically significant movements. Early scholarship labored to surmount the same methodological obstacles faced by modern scholars, notably scarce documentation, but still produced pathbreaking studies such as W. E. B. Du Bois'sThe Philadelphia Negro, Carter Woodson'sA Century of Negro Migration, and Clyde Kiser'sSea Island to City. Modern scholarship since the 1950s falls into eight distinct genres. An assessment of representative works in each genre reveals a variety of configurations of strengths and weaknesses, while offering guidelines for future research.
Including orbital fluctuations in the noise spectrum of autonomous circuits
Authors: Traversa Fabio L. , Bonani Fabrizio
Published: January 2011

We discuss the impact of orbital fluctuations on the noise spectrum of a free-running oscillator, exploiting a rigorous nonlinear perturbative analysis based on the Floquet theory, and providing evidence of its relevance for high-Q oscillators.
Erratum: Dating the cyanobacterial ancestor of the chloroplast
Authors: Falcón Luisa I , Magallón Susana , Castillo Amanda
Published: January 2011

Correction to: The ISME Journal (2010) 6, 777–783; doi:10.1038/ismej.2010.2 Since the publication of this paper, the authors have noticed an omission in the acknowledgements section. The missing text is as follows. LIF, SM and AC were funded by SEP-CONACyT (Mexico), projects no. 56045 (LIF) and 2004-C01-46475-Q (SM, AC), respectively.
Multireference composite approaches for the accurate study of ground and excited electronic states: C2, N2, and O2
Authors: Jiang Wanyi , Wilson Angela K.
Published: January 2011

A multireference analog of the correlation consistent composite approach (MR-ccCA) based on complete active space with second-order perturbation theory (CASPT2) has been utilized in an investigation of the ground and valence excited states of C2, N2, and O2. The performance of different second-order multireference perturbation theory methods including second-order n-electron valence state perturbation theory, second-order multireference Møller–Plesset, and second-order generalized van Vleck perturbation theory has been analyzed as potential alternatives to CASPT2 within MR-ccCA. The MR-ccCA-P predicts spectroscopic constants with overall mean absolute deviations from experimental values of 0.0006 Å, 7.0 cm−1, and 143 cm−1 for equilibrium bond length (re), harmonic frequency (ωe), and term values (Te), respectively, which are comparable to the predictions by more computationally costly multireference configuration interaction-based methods.
Dynamic coupling between the LID and NMP domain motions in the catalytic conversion of ATP and AMP to ADP by adenylate kinase
Authors: Jana Biman , Adkar Bharat V. , Biswas Rajib , Bagchi Biman
Published: January 2011

The catalytic conversion of adenosine triphosphate (ATP) and adenosine monophosphate (AMP) to adenosine diphosphate (ADP) by adenylate kinase (ADK) involves large amplitude, ligand induced domain motions, involving the opening and the closing of ATP binding domain (LID) and AMP binding domain (NMP) domains, during the repeated catalytic cycle. We discover and analyze an interesting dynamical coupling between the motion of the two domains during the opening, using large scale atomistic molecular dynamics trajectory analysis, covariance analysis, and multidimensional free energy calculations with explicit water. Initially, the LID domain must open by a certain amount before the NMP domain can begin to open. Dynamical correlation map shows interesting cross-peak between LID and NMP domain which suggests the presence of correlated motion between them. This is also reflected in our calculated two-dimensional free energy surface contour diagram which has an interesting elliptic shape, revealing a strong correlation between the opening of the LID domain and that of the NMP domain. Our free energy surface of the LID domain motion is rugged due to interaction with water and the signature of ruggedness is evident in the observed root mean square deviation variation and its fluctuation time correlation functions. We develop a correlated dynamical disorder-type theoretical model to explain the observed dynamic coupling between the motion of the two domains in ADK. Our model correctly reproduces several features of the cross-correlation observed in simulations.
Note: Scalable multiphoton coincidence-counting electronics
Authors: Branning D. , Khanal S. , Shin Y. H. , Clary B. , Beck M.
Published: January 2011

We present a multichannel coincidence-counting module for use in quantum optics experiments. The circuit takes up to four transistor–transistor logic pulse inputs and counts either twofold, threefold, or fourfold coincidences, within a user-selected coincidence-time window as short as 12 ns. The module can accurately count eight sets of multichannel coincidences, for input rates of up to 84 MHz. Due to their low cost and small size, multiple modules can easily be combined to count arbitrary M-order coincidences among N inputs.
Explicit correlation and intermolecular interactions: Investigating carbon dioxide complexes with the CCSD(T)-F12 method
Authors: de Lange Katrina M. , Lane Joseph R.
Published: January 2011

We have optimized the lowest energy structures and calculated interaction energies for the CO2–Ar, CO2–N2, CO2–CO, CO2–H2O, and CO2–NH3 dimers with the recently developed explicitly correlated coupled cluster singles doubles and perturbative triples [CCSD(T)]-F12 methods and the associated VXZ-F12 (where X = D,T,Q) basis sets. For a given cardinal number, we find that results obtained with the CCSD(T)-F12 methods are much closer to the CCSD(T) complete basis set limit than the conventional CCSD(T) results. The relatively modest increase in the computational cost between explicit and conventional CCSD(T) is more than compensated for by the impressive accuracy of the CCSD(T)-F12 method. We recommend use of the CCSD(T)-F12 methods in combination with the VXZ-F12 basis sets for the accurate determination of equilibrium geometries and interaction energies of weakly bound electron donor acceptor complexes.
Anomalous strong exchange narrowing in excitonic systems
Authors: Roden Jan , Eisfeld Alexander
Published: January 2011

We investigate theoretically the phenomenon of exchange narrowing in the absorption spectrum of a chain of monomers, which are coupled via resonant dipole–dipole interaction. The individual (uncoupled) monomers exhibit a broad absorption line shape due to the coupling to an environment consisting of a continuum of vibrational modes. Upon increasing the interaction between the monomers, the absorption spectrum of the chain narrows. For a non-Markovian environment with a Lorentzian spectral density, we find a narrowing of the peak width [full width at half maximum (FWHM)] by a factor 1/N, where N is the number of monomers. This is much stronger than the usual \documentclass[12pt]{minimal}\begin{document}$1/\sqrt{N}$\end{document}1/N narrowing. Furthermore, it turns out that for a Markovian environment no exchange narrowing at all occurs. The relation of different measures of the width (FWHM, standard deviation) is discussed.
Density matrix based microscopic theory of molecule metal–nanoparticle interactions: Linear absorbance and plasmon enhancement of intermolecular excitation energy transfer
Authors: Kyas Gerold , May Volkhard
Published: January 2011

A microscopic theory of interacting molecule metal–nanoparticle (MNP) systems is presented and used to compute absorption spectra and the plasmon enhancement of intermolecular excitation energy transfer (EET). The approach is based on a nonperturbative consideration of the Coulomb coupling matrix elements responsible for EET between the molecules and the MNP. In this way, the need to determine the local fields induced by surface plasmon excitations of the MNP is removed, but the whole description is restricted to distances among the interacting species less than the wavelength of absorbed photons. Based on a density matrix theory, the approach accounts for the vibrational level structure of the molecules, intramolecular vibrational energy redistribution (IVR), and plasmon damping. Numerical results for linear absorbance spectra and EET dynamics are offered. In this respect the importance of energy dissipation in the MNP due to rapid surface plasmon decay is emphasized.
Contactless electroreflectance of polar and nonpolar GaN/AlGaN quantum wells
Authors: Kudrawiec R. , Gladysiewicz M. , Dussaigne A. , Teisseyre H. , Boćkowski M. , Grzegory I. , Suski T. , Misiewicz J. , Grandjean N.
Published: January 2011

Contactless electroreflectance (CER) has been applied to study optical transitions between the ground and excited states in polar and a-plane nonpolar 2 nm wide GaN/Al0.12Ga0.88N quantum well (QW) structures. In addition to the fundamental transition, CER features related to optical transitions between excited states were clearly observed for the polar QW structure whereas such features were not observed for the nonpolar QW structure. This experimental result clearly shows that the polarization-related electric field leads to a quantum confinement of some extra states in the polar QW system. Such states are not confined in the nonpolar QW and, therefore, optical transitions between them are not detected, i.e., only the fundamental transition is observed in CER spectrum of the nonpolar QW.
Optical recording mechanisms in undoped titanosillenite crystals
Authors: Jerez Vladimir , de Oliveira Ivan , Frejlich Jaime
Published: January 2011

We show that optical recording in undoped photorefractive titanosillenite Bi12TiO20 (BTO) crystals involve electrons, holes and ions, depending on the experimental conditions. Holographic recording and erasure at higher than room temperature was carried out on an undoped crystal sample, showing the presence of a fast photosensitive electron-based hologram and a slower compensating one of nonphotosensitive nature that is responsible for hologram fixing in BTO and is likely to be based on H+ ions. The fixed grating showed a diffraction eficiency η≈0.002 and a characteristic activation energy of 0.85±0.05 eV. A strong light-induced (darkening) photochromic effect was also detected, that had to be accounted on for diffraction efficiency measurement. Holes are shown to participate in the optical recording process when selectively photoexcited with infrared light.
High electron mobility due to sodium ions in the gate oxide of SiC-metal-oxide-semiconductor field-effect transistors
Authors: Tuttle B. R. , Dhar S. , Ryu S.-H. , Zhu X. , Williams J. R. , Feldman L. C. , Pantelides S. T.
Published: January 2011

Oxidation of SiC with the incorporation of Na in the gate oxide was recently found to lead to significantly enhanced electron mobilities in the SiC inversion layer but the underlying mechanism has remained elusive. Here, we report a combination of density functional first-principles calculations and experiments. The new findings demonstrate that neutral Na is essentially a spectator impurity that occupies near interfacial interstitial sites and does not interact with the interface or with interfacial defects. Na ions, however, introduce an effective mass hydrogenic impurity band at the edge of the SiC conduction band that can account for the observed effects.
Plasmonic metamaterials for ultrasensitive refractive index sensing at near infrared
Authors: Gu Yang , Li Qiuze , Xiao Jie , Wu Kedi , Wang Guo Ping
Published: January 2011

We experimentally report a kind of plasmonic metamaterials for high sensitive refractive index sensing. The metamaterials are an X-shaped metal nanohole array fabricated by holographic lithography followed by electron-beam evaporation and lift-off procedure. Transmission spectrum measurements reveal that the localized surface plasmon resonance (LSPR) wavelength of such nanohole array shows ultrasensitive response to refractive index change in the surrounding medium. A sensitivity of 1398 nm per refractive index unit is achieved at near infrared. The high sensitivity is attributed to the well confined and greatly enhanced electric field created by LSPR as well as the increased spatial overlap between the localized electric field and the surrounding medium. The robust fabrication technique and high sensitivity provide the present plasmonic metamaterials great potentials for the development of chip-based high sensitive nanooptical biomedicine sensors and integrated devices.
A systematic study of (NH4)2S passivation (22%, 10%, 5%, or 1%) on the interface properties of the Al2O3/In0.53Ga0.47As/InP system for n-type and p-type In0.53Ga0.47As epitaxial layers
Authors: O’Connor É. , Brennan B. , Djara V. , Cherkaoui K. , Monaghan S. , Newcomb S. B. , Contreras R. , Milojevic M. , Hughes G. , Pemble M. E. , Wallace R. M. , Hurley P. K.
Published: January 2011

In this work, we present the results of an investigation into the effectiveness of varying ammonium sulphide (NH4)2S concentrations in the passivation of n-type and p-type In0.53Ga0.47As. Samples were degreased and immersed in aqueous (NH4)2S solutions of concentrations 22%, 10%, 5%, or 1% for 20 min at 295 K, immediately prior to atomic layer deposition of Al2O3. Multi-frequency capacitance-voltage (C-V) results on capacitor structures indicate that the lowest frequency dispersion over the bias range examined occurs for n-type and p-type devices treated with the 10%(NH4)2S solution. The deleterious effect on device behavior of increased ambient exposure time after removal from 10%(NH4)2S solution is also presented. Estimations of the interface state defect density (Dit) for the optimum 10%(NH4)2S passivated In0.53Ga0.47As devices extracted using an approximation to the conductance method, and also extracted using the temperature-modified high-low frequency C-V method, indicate that the same defect is present over n-type and p-type devices having an integrated Dit of ∼2.5×1012 cm−2 (±1×1012 cm−2) with the peak density positioned in the middle of the In0.53Ga0.47As band gap at approximately 0.37 eV (±0.03 eV) from the valence band edge. Both methods used for extracting Dit show very good agreement, providing evidence to support that the conductance method can be applied to devices incorporating high-k oxides on In0.53Ga0.47As.
Electron spin relaxation in intrinsic bulk InP semiconductor
Authors: Ma Hong , Jin Zuanming , Wang Lihua , Ma Guohong
Published: January 2011

Electron spin dynamics in intrinsic bulk indium phosphide (InP) semiconductor is studied by time resolved pump probe reflectivity technique using the cocircularly and countercircularly polarized femtosecond pulses at room temperature and 70 K. The reflectivity change from bleaching into absorption is observed with increasing pump photon energy, which can be explained in terms of the spin sensitive band filling and band gap renormalization effects. Density dependence of electron spin relaxation time shows similar tendency at room temperature and 70 K. With increasing carrier density, the electron spin relaxation time increases and then decreases after reaching a maximum value. Our experimental results agree well with the recent theoretical prediction [Jiang and Wu, Phys. Rev. B 79, 125206 (2009)] and D’yakonov–Perel’ mechanism is considered as a dominating contribution to the electron spin relaxation in intrinsic bulk InP semiconductor.
Correlation between structure and electrical transport in ion-irradiated graphene grown on Cu foils
Authors: Buchowicz Grant , Stone Peter R. , Robinson Jeremy T. , Cress Cory D. , Beeman Jeffrey W. , Dubon Oscar D.
Published: January 2011

Graphene grown by chemical vapor deposition and supported on SiO2 and sapphire substrates was studied following the controlled introduction of defects induced by 35 keV carbon ion irradiation. Changes in Raman spectra for fluences ranging from 1012 to 1015 cm−2 indicate that the structure of graphene evolves from a highly ordered layer, to a patchwork of disordered domains, to an essentially amorphous film. These structural changes result in a dramatic decrease in the Hall mobility by orders of magnitude while, remarkably, the Hall concentration remains almost unchanged, suggesting that the Fermi level is pinned at a hole concentration near 1×1013 cm−2. A model for scattering by resonant scatterers is in good agreement with mobility measurements up to an ion fluence of 1×1014 cm−2.
Efficient organic light-emitting devices with platinum-complex emissive layer
Authors: Yang Xiaohui , Wu Fang-Iy , Haverinen Hanna , Li Jian , Cheng Chien-Hong , Jabbour Ghassan E.
Published: January 2011

We report efficient organic light-emitting devices having a platinum-complex emissive layer with the peak external quantum efficiency of 17.5% and power efficiency of 45 lm W−1. Variation in the device performance with platinum-complex layer thickness can be attributed to the interplay between carrier recombination and intermolecular interactions in the layer. Efficient white devices using double platinum-complex layers show the external quantum efficiency of 10%, the Commission Internationale d’Énclairage coordinates of (0.42, 0.41), and color rendering index of 84 at 1000 cd m−2.
Interface-modified random circuit breaker network model applicable to both bipolar and unipolar resistance switching
Authors: Lee S. B. , Lee J. S. , Chang S. H. , Yoo H. K. , Kang B. S. , Kahng B. , Lee M.-J. , Kim C. J. , Noh T. W.
Published: January 2011

We observed reversible-type changes between bipolar (BRS) and unipolar resistance switching (URS) in one Pt/SrTiOx/Pt capacitor. To explain both BRS and URS in a unified scheme, we introduce the “interface-modified random circuit breaker network model,” in which the bulk medium is represented by a percolating network of circuit breakers. To consider interface effects in BRS, we introduce circuit breakers to investigate resistance states near the interface. This percolation model explains the reversible-type changes in terms of connectivity changes in the circuit breakers and provides insights into many experimental observations of BRS which are under debate by earlier theoretical models.
Nitrogen and carbon isotope fractionations of zooplankton consumers in ponds: potential effects of seston C:N stoichiometry
Authors: Doi Hideyuki , Chang Kwang-Hyeon , Nakano Shin-ichi
Published: January 2011

C : N stoichiometry in food sources is known to influence nitrogen isotope fractionation of consumers, but the relationship between C : N stoichiometry and isotope fractionation has never been tested in the field. In this study, we investigated the effects of the C : N ratio of food sources on nitrogen and carbon isotope fractionation (Δδ15N and Δδ13C) of consumers, using zooplankton communities in 15 ponds in Japan. The fractionation variations we found contradicted the assumption of a 3.4‰ enrichment in δ15N of consumers per trophic level. However, the negative relationships between Δδ15N of filter-feeding zooplankton and the C : N ratio of seston supported the isotope homeostasis hypothesis, which predicts isotopic homeostasis of consumers to vary with respect to their body nutrient composition. The Δδ15N of Eodiaptomus sp. and cyclopoid copepods did not correlate with the C : N ratio of the seston. Further studies should pay attention to the isotope fractionation of consumers in the field, especially given the increased use of isotope fractionation to elucidate the structure of natural food webs.
Size at maturity and reproductive traits of shortfin mako, Isurus oxyrinchus, in the western and central North Pacific
Authors: Semba Yasuko , Aoki Ichiro , Yokawa Kotaro
Published: January 2011

Shortfin mako, Isurus oxyrinchus, is a highly migratory shark with a worldwide distribution. Despite recent global concern and intensive ecological studies on this species, little is known about its reproduction, owing to a paucity of information on mature females. We investigated the size-at-maturity and reproductive traits of shortfin mako in the western and central North Pacific. Males attain maturity at a much smaller size (156 cm) than females (256 cm). The positive relationship between maternal size and litter size indicates that fecundity increases as the female grows. The seasonal trends in the gonadosomatic index of mature individuals and the presence of females in early pregnancy confirmed that mating occurs from spring to summer. From monthly changes in embryonic body lengths, averaged per litter, and the seasonal occurrence of neonates, we infer that parturition occurs from winter to spring and the gestation period is 9–13 months. There was a negative correlation between embryonic developmental stages and environmental temperature for females in various stages of pregnancy. The productivity of this species may be higher than previously thought, considering the estimated gestation period and size-related fecundity.
Can large branchiopods shape microcrustacean communities in Mediterranean temporary wetlands?
Authors: Waterkeyn Aline , Grillas Patrick , Anton-Pardo Maria , Vanschoenwinkel Bram , Brendonck Luc
Published: January 2011

It was recently suggested that large branchiopods may play a keystone role in temporary aquatic habitats. Using a microcosm experiment manipulating microcrustacean communities of Mediterranean temporary wetlands (Camargue, Southern France), we tested the following hypotheses: (i) large branchiopods (the notostracan Triops cancriformis and the anostracan Chirocephalus diaphanus) can limit microcrustacean densities through both competition and predation; (ii) notostracans create high suspended-matter concentrations through bioturbation, which can negatively impact microcrustaceans; and (iii) the outcome of these biotic interactions is more detrimental at high salinities. We found a strong predatory impact of T. cancriformis on active microcrustacean populations, but also on dormant populations through the consumption of resting eggs. They also preyed on anostracans and their conspecifics and can indirectly have a negative effect on microcrustaceans through bioturbation, probably by impeding filtering capacities. The presence of C. diaphanus also limited most microcrustacean groups, probably through competition and/or predation. We did not find a significant effect of the tested salinity range (0.5–2.5 g L–1) on the biotic interactions. Our study shows that large branchiopods can shape microcrustacean communities under a wide range of environmental conditions and confirms their potential for a keystone role, especially one of notostracans as top predators.
Surface chemistry: Key to control and advance myriad technologies
Authors: Yates John T. , Campbell Charles T.
Published: January 2011

This special issue on surface chemistry is introduced with a brief history of the field, a summary of the importance of surface chemistry in technological applications, a brief overview of some of the most important recent developments in this field, and a look forward to some of its most exciting future directions. This collection of invited articles is intended to provide a snapshot of current developments in the field, exemplify the state of the art in fundamental research in surface chemistry, and highlight some possibilities in the future. Here, we show how those articles fit together in the bigger picture of this field.
Neural integrity is maintained by dystrophin inC. elegans
Authors: Zhou Shan , Chen Lihsia
Published: January 2011

The dystrophin protein complex (DPC), composed of dystrophin and associated proteins, is essential for maintaining muscle membrane integrity. The link between mutations in dystrophin and the devastating muscle failure of Duchenne’s muscular dystrophy (DMD) has been well established. Less well appreciated are the accompanying cognitive impairment and neuropsychiatric disorders also presented in many DMD patients, which suggest a wider role for dystrophin in membrane–cytoskeleton function. This study provides genetic evidence of a novel role for DYS-1/dystrophin in maintaining neural organization in Caenorhabditis elegans. This neuronal function is distinct from the established role of DYS-1/dystrophin in maintaining muscle integrity and regulating locomotion. SAX-7, an L1 cell adhesion molecule (CAM) homologue, and STN-2/γ-syntrophin also function to maintain neural integrity in C. elegans. This study provides biochemical data that show that SAX-7 associates with DYS-1 in an STN-2/γ-syntrophin–dependent manner. These results reveal a recruitment of L1CAMs to the DPC to ensure neural integrity is maintained.
ATR-mediated phosphorylation of DNA polymerase η is needed for efficient recovery from UV damage
Authors: Göhler Thomas , Sabbioneda Simone , Green Catherine M. , Lehmann Alan R.
Published: January 2011

DNA polymerase η (polη) belongs to the Y-family of DNA polymerases and facilitates translesion synthesis past UV damage. We show that, after UV irradiation, polη becomes phosphorylated at Ser601 by the ataxia-telangiectasia mutated and Rad3-related (ATR) kinase. DNA damage–induced phosphorylation of polη depends on its physical interaction with Rad18 but is independent of PCNA monoubiquitination. It requires the ubiquitin-binding domain of polη but not its PCNA-interacting motif. ATR-dependent phosphorylation of polη is necessary to restore normal survival and postreplication repair after ultraviolet irradiation in xeroderma pigmentosum variant fibroblasts, and is involved in the checkpoint response to UV damage. Taken together, our results provide evidence for a link between DNA damage–induced checkpoint activation and translesion synthesis in mammalian cells.
Controlling voltage step-up ratio of Rosen-type transformer based on magnetoelectric coupling
Authors: Lv Li , Zhou Jian-Ping , Guo Yang-Yang , Liu Peng , Zhang Huai-Wu
Published: January 2011

We proposed a magnetoelectric (ME) composite transformer by bonding a Rosen-type transformer and a Terfenol-D plate, whose voltage step-up ratio could be controlled by an applied magnetic field. When applying a sine signal on the input port of the transformer, an amplifying signal was produced at the output port because of the amplifying effect. Meanwhile, a magnetization was induced in the magnetostrictive part due to the converse ME coupling, and then a voltage at the output port due to the direct ME effect. Superimposition of the ME signal on the amplifying signal resulted that the voltage step-up ratio of the composite transformer could be controlled by the applied magnetic field. In addition, electric-field-induced magnetization in Terfenol-D is very strong, which was dominated by the stress in the composite transformer.
High-quality Ge/Si0.4Ge0.6 multiple quantum wells for photonic applications: growth by reduced pressure chemical vapour deposition and structural characteristics
Authors: Liu Xue-Chao , Myronov M , Dobbie A , Morris R J H , Leadley D R
Published: January 2011

Strain-symmetrized Ge/SiGe multiple quantum wells have been grown on a thin (2.1 µm) relaxed Si0.2Ge0.8/Ge/Si(1 0 0) virtual substrate (VS) by reduced pressure chemical vapour deposition. Such structures are of interest in optoelectronic applications for which the structural integrity of the quantum well layers, after processing, is critical. The layer composition, thickness and interface quality have been studied for wafers both as-grown and after annealing between 550 and 700 °C. Transmission electron microscopy indicated precise thickness control of ±0.1 nm and sharp abruptness between the Ge QWs and SiGe barrier layers. A smooth surface was observed, with an average rms roughness of 1.5 ± 0.1 nm determined by atomic force microscopy. High-resolution x-ray diffraction (HR-XRD) indicated that both the QWs and barriers were fully strained compared with the relaxed VS. The thermal stability of the epilayers was investigated both by ultra low energy secondary ion mass spectroscopy of post-growth annealed layers and by in situ annealing in a high temperature HR-XRD stage. No obvious interdiffusion and strain relaxation was observed provided the annealing temperature was below 600 °C, but significant atomic rearrangement was evident for greater thermal budgets, thereby setting an upper processing temperature for this type of structure.