bluuebunny/crossref_metadata_2025 huggingface dataset:
Scripts de atendimento em call centers: uma visão de documentos eletrônicos
Authors: Silveira Sandra Maria , Moura Maria Aparecida
Published: August 2011

O presente artigo contextualiza o serviço de atendimento aos clientes (SAC) no âmbito da Ciência da Informação e busca compreender o fenômeno sob o enfoque da organização e do uso da informação. Analisa-se o processo informacional dos serviços de atendimento aos clientes realizados em call centers, com o foco na organização e no uso das bases de informação tendo em vista a sistematização de parâmetros para subsidiarem a criação, a manutenção e a validação dos scripts de atendimento. Scripts são documentos eletrônicos que contêm orientação para executar procedimentos relativos a produtos e serviços da instituição e na interação com os consumidores. Por fim, identificaram-se os atributos de qualidade de informação que orientam a construção e a manutenção das bases de informações e sistematizaram-se os parâmetros para elaboração das bases de informações em consonância com os processos de organização e uso da informação no âmbito do SAC.
The kinetics and mechanism of an aqueous phase isoprene reaction with hydroxyl radical
Authors: Huang D. , Zhang X. , Chen Z. M. , Zhao Y. , Shen X. L.
Published: August 2011

Abstract. Aqueous phase chemical processes of organic compounds in the atmosphere have received increasing attention, partly due to their potential contribution to the formation of secondary organic aerosol (SOA). Here, we analyzed the aqueous OH-initiated oxidation of isoprene and its reaction products including carbonyl compounds and organic acids, regarding the acidity and temperature as in-cloudy conditions. We also performed a laboratory simulation to improve our understanding of the kinetics and mechanisms for the products of aqueous isoprene oxidation that are significant precursors of SOA; these included methacrolein (MACR), methyl vinyl ketone (MVK), methyl glyoxal (MG), and glyoxal (GL). We used a novel chemical titration method to monitor the concentration of isoprene in the aqueous phase. We used a box model to interpret the mechanistic differences between aqueous and gas phase OH radical-initiated isoprene oxidations. Our results were the first demonstration of the rate constant for the reaction between isoprene and OH radical in water, 1.2 ± 0.4) × 1010 M−1 s−1 at 283 K. Molar yields were determined based on consumed isoprene. Of note, the ratio of the yields of MVK (24.1 ± 0.8 %) to MACR (10.9 ± 1.1%) in the aqueous phase isoprene oxidation was approximately double that observed for the corresponding gas phase reaction. We hypothesized that this might be explained by a water-induced enhancement in the self-reaction of a hydroxy isoprene peroxyl radical (HOCH2C(CH3)(O2)CH = CH2) produced in the aqueous reaction. The observed yields for MG and GL were 11.4 ± 0.3 % and 3.8 ± 0.1 %, respectively. Model simulations indicated that several potential pathways may contribute to the formation of MG and GL. Finally, oxalic acid increased steadily throughout the course of the study, even after isoprene was consumed completely. The observed yield of oxalic acid was 26.2 ± 0.8 % at 6 h. The observed carbon balance accounted for ~50 % of the consumed isoprene. The presence of high-molecular-weight compounds may have accounted for a large portion of the missing carbons, but they were not quantified in this study. In summary, our work has provided experimental evidence that the availably abundant water could affect the distribution of oxygenated organic compounds produced in the oxidation of volatile organic compounds.
High-resolution simulations of atmospheric CO2 over complex terrain – representing the Ochsenkopf mountain tall tower
Authors: Pillai D. , Gerbig C. , Ahmadov R. , Rödenbeck C. , Kretschmer R. , Koch T. , Thompson R. , Neininger B. , Lavrié J. V.
Published: August 2011

Abstract. Accurate simulation of the spatial and temporal variability of tracer mixing ratios over complex terrain is challenging, but essential in order to utilize measurements made in complex orography (e.g. mountain and coastal sites) in an atmospheric inverse framework to better estimate regional fluxes of these trace gases. This study investigates the ability of high-resolution modeling tools to simulate meteorological and CO2 fields around Ochsenkopf tall tower, situated in Fichtelgebirge mountain range- Germany (1022 m a.s.l.; 50°1′48" N, 11°48′30" E). We used tower measurements made at different heights for different seasons together with the measurements from an aircraft campaign. Two tracer transport models – WRF (Eulerian based) and STILT (Lagrangian based), both with a 2 km horizontal resolution – are used together with the satellite-based biospheric model VPRM to simulate the distribution of atmospheric CO2 concentration over Ochsenkopf. The results suggest that the high-resolution models can capture diurnal, seasonal and synoptic variability of observed mixing ratios much better than coarse global models. The effects of mesoscale transports such as mountain-valley circulations and mountain-wave activities on atmospheric CO2 distributions are reproduced remarkably well in the high-resolution models. With this study, we emphasize the potential of using high-resolution models in the context of inverse modeling frameworks to utilize measurements provided from mountain or complex terrain sites.
Absorbing aerosol in the troposphere of the Western Arctic during the 2008 ARCTAS/ARCPAC airborne field campaigns
Authors: McNaughton C. S. , Clarke A. D. , Freitag S. , Kapustin V. N. , Kondo Y. , Moteki N. , Sahu L. , Takegawa N. , Schwarz J. P. , Spackman J. R. , Watts L. , Diskin G. , Podolske J. , Holloway J. S. , Wisthaler A. , Mikoviny T. , de Gouw J. , Warneke C. , Jimenez J. , Cubison M. , Howell S. G. , Middlebrook A. , Bahreini R. , Anderson B. E. , Winstead E. , Thornhill K. L. , Lack D. , Cozic J. , Brock C. A.
Published: August 2011

Abstract. In the spring of 2008 NASA and NOAA funded the ARCTAS and ARCPAC field campaigns as contributions to POLARCAT, a core IPY activity. During the campaigns the NASA DC-8, P-3B and NOAA WP-3D aircraft conducted over 160 h of in-situ sampling between 0.1 and 12 km throughout the Western Arctic north of 55° N (i.e. Alaska to Greenland). All aircraft were equipped with multiple wavelength measurements of aerosol optics, trace gas and aerosol chemistry measurements, as well as direct measurements of the aerosol size distributions and black carbon mass. Late April of 2008 proved to be exceptional in terms of Asian biomass burning emissions transported to the Western Arctic. Though these smoke plumes account for only 11–14 % of the samples within the Western Arctic domain, they account for 42–47 % of the total burden of black carbon. Dust was also commonly observed but only contributes to 4–12 % and 3–8 % of total light absorption at 470 and 530 nm wavelengths above 6 km. Below 6 km, light absorption by carbonaceous aerosol derived from urban/industrial and biomass burning emissions account for 97–99 % of total light absorption by aerosol. Stratifying the data to reduce the influence of dust allows us to determine mass absorption efficiencies for black carbon of 11.2±0.8, 9.5±0.6 and 7.4±0.7 m2 g−1 at 470, 530 and 660 nm wavelengths. These estimates are consistent with 35–80 % enhancements in 530 nm absorption due to clear or slightly absorbing coatings of pure black carbon particulate. Assuming a 1/λ wavelength dependence for BC absorption, and assuming that refractory aerosol (420 °C, τ = 0.1 s) in low-dust samples is dominated by brown carbon, we derive mass absorption efficiencies for brown carbon of 0.83±0.15 and 0.27±0.08 m2 g−1 at 470 and 530 nm wavelengths. Estimates for the mass absorption efficiencies of Asian dust are 0.034 m2 g−1 and 0.017 m2 g−1. However the absorption efficiency estimates for dust are highly uncertain due to the limitations imposed by PSAP instrument noise. In-situ ARCTAS/ARCPAC measurements during the IPY provide valuable constraints for absorbing aerosol over the Western Arctic, species which are currently poorly simulated over a region that is critically under-sampled.
Remote atomic clock synchronization via satellites and optical fibers
Authors: Piester D. , Rost M. , Fujieda M. , Feldmann T. , Bauch A.
Published: August 2011

Abstract. In the global network of institutions engaged with the realization of International Atomic Time (TAI), atomic clocks and time scales are compared by means of the Global Positioning System (GPS) and by employing telecommunication satellites for two-way satellite time and frequency transfer (TWSTFT). The frequencies of the state-of-the-art primary caesium fountain clocks can be compared at the level of 10−15 (relative, 1 day averaging) and time scales can be synchronized with an uncertainty of one nanosecond. Future improvements of worldwide clock comparisons will require also an improvement of the local signal distribution systems. For example, the future ACES (atomic clock ensemble in space) mission shall demonstrate remote time scale comparisons at the uncertainty level of 100 ps. To ensure that the ACES ground instrument will be synchronized to the local time scale at the Physikalisch-Technische Bundesanstalt (PTB) without a significant uncertainty contribution, we have developed a means for calibrated clock comparisons through optical fibers. An uncertainty below 40 ps over a distance of 2 km has been demonstrated on the campus of PTB. This technology is thus in general a promising candidate for synchronization of enhanced time transfer equipment with the local realizations of Coordinated Universal Time UTC. Based on these experiments we estimate the uncertainty level for calibrated time transfer through optical fibers over longer distances. These findings are compared with the current status and developments of satellite based time transfer systems, with a focus on the calibration techniques for operational systems.
Berechnung von Nichtlinearitätsparametern von RF MOS Mischern mittels Volterra-Reihen
Authors: Susic A. , Darrat A. H. , Mathis W.
Published: August 2011

Abstract. Die Nichtlinearität einer Mischerschaltung bezüglich des Informationssignals führt zu unerwünschten Spektralanteilen am Ausgang des Mischers. Da nicht alle Spektralanteile kritisch sind, müssen bei einer Nichtlinearitätsanalyse nur bestimmte Spektralanteile ermittelt werden. In dieser Arbeit wird ein Verfahren zur Bestimmung der Spektralanteile der Zustandsgrößen im Mischer mit Hilfe der Volterra-Reihe gezeigt. Das Verfahren basiert auf die Methode der nichtlinearen Stromquellen. Es wird sowohl auf nicht-schaltende als auch schaltende Mischer angewendet. Hierbei wird der erste als ein zeitinvariantes System mit zwei Eingängen und der zweite als ein periodisch zeitvariantes System mit einem Eingang modelliert. Das Verfahren wird in dem Computeralgebraprogramm MAPLE für den einfach balancierten MOS Mischer implementiert. Es ermöglicht die Herleitung von semi-symbolischen Ausdrücken für die Spektralanteile in Abhängigkeit von den Entwurfsparametern. Die numerischen Ergebnisse des Verfahrens werden gegenüber Simulationen mit SpectreRF verglichen.
A multi channel coupling based approach for the prediction of the channel capacity of MIMO-systems
Authors: Hagebölling F. , Zölzer U.
Published: August 2011

Abstract. When installing Multiple Input Multiple Output (MIMO)-systems, the antenna positioning has a major influence upon the achievable transmission quality. To determine those antenna positions, which maximize the transmission quality, in adequate time, a computer based prediction of the channel capacity is imperative. In this paper, we will show that Ray Tracing, which is a very popular prediction method and well suited for the prediction of transfer functions or power delay profiles, produces unacceptable errors when predicting the channel capacity of MIMO-systems. Furthermore we identify the source of the prediction errors and present a new algorithm, based on an approach known as Multi Channel Coupling (MCC), which avoids this error source. Finally a comparison of the prediction results of our algorithm with prediction results gained with an Image Ray Tracer as well as with measured results is used to show the formidable increasement of prediction accuracy which can be gained by using our algorithm.
Physical layer simulation results for IEEE 802.15.3c with different channel models
Authors: Liso Nicolás M. , Jacob M. , Kürner T.
Published: August 2011

Abstract. This paper investigates the performance of the 60 GHz IEEE 802.15.3c physical layer (PHY) specification in terms of bit error rate (BER) against signal to noise ratio. Two PHY modes of the standard have been implemented and simulated, i.e., Single Carrier and High Speed Interface. The first mode uses single carrier (SC) block transmission and the second mode uses orthogonal frequency division multiplexing (OFDM). One of the main issues in the new 60 GHz standards is multipath propagation, which plays an important role in the link quality. Thus, we have tested the PHY with the IEEE standard channel model, ray tracing simulations and real 60 GHz measurements.
Anwendung einer Switched-System Modellierung zur Stabilitätsanalyse von zeitkontinuierlichen singlebit ΣΔ-Wandlern
Authors: Stegemann S. , Zorn C. , Brückner T. , Ortmanns M. , Mathis W.
Published: August 2011

Abstract. Im Hinblick auf die Optimierung von zeitkontinuierlichen ΣΔ-Wandlern ist ein genaues Verständnis der dynamischen Eigenschaften des Systems von essentieller Bedeutung. In dieser Arbeit wird der ΣΔ-Modulator dafür in die Klasse der Mixed-Signal Systeme eingeordnet und als Übertragungssystem mit geschalteter Rückkopplung betrachtet. Mit diesem Switched-System-Modell können unter Zuhilfenahme einer geeigneten Zustandsraumdarstellung die Signalamplituden der internen Integratoren sowie die Maximalamplitude am Quantisierereingang bestimmt werden. Unter Verwendung einer Worst-Case Analyse ist es damit möglich, Aussagen über den Aussteuerbereich der Integratoren sowie der maximal stabilen Eingangsamplitude zu treffen. Die Vorgehensweise wird anhand eines Beispielmodulators dargestellt.
Reliability analysis of buffer stage in mixed signal application
Authors: More S. , Fulde M. , Chouard F. , Schmitt-Landsiedel D.
Published: August 2011

Abstract. This paper discusses reliability analysis of a buffer circuit targeted for an analog to digital converter application. The circuit designed in a 32 nm high-κ metal gate CMOS technology was investigated by circuit simulation and sensitivity analysis. This analysis was conducted for realistic time varying (AC) stress. As aging effects, negative and positive bias temperature instability, conducting and non-conducting hot carrier injection are taken into consideration. The aging contributions of these effects on the different transistors in the buffer circuit and on different buffer performance figures are evaluated. Using these results, the impact of an aged buffer circuit on the performance of a successive approximation ADC circuit is evaluated. The most severely affected performance due to aging is amplifier offset, which leads to time varying gain error in the ADC circuit.
Network model of on-chip antennas
Authors: Mukhtar F. , Yordanov H. , Russer P.
Published: August 2011

Abstract. A Network model of an ultra-wide band, intra-chip wireless link is presented. Numerical data of Z-parameters, obtained from full wave simulation of the structure, are used to obtain a rational function representation via the Vector Fitting procedure. Brune's circuit synthesis is applied to generate the network model from rational functions.
Countermeasures against NBTI degradation on 6T-SRAM cells
Authors: Glocker E. , Schmitt-Landsiedel D. , Drapatz S.
Published: August 2011

Abstract. In current process technologies, NBTI (negative bias temperature instability) has the most severe aging effect on static random access memory (SRAM) cells. This degradation effect causes loss of stability. In this paper countermeasures against this hazard are presented and quantified via simulations in 90 nm process technologies by the established metrics SNMread, SNMhold, Iread and Write Level. With regard to simulation results and practicability best candidates are chosen and, dependent on individual preferences at memory cell design, the best countermeasure in each case is recommended.
A modified prefix operator well suited for area-efficient brick-based adder implementations
Authors: Rust I. , Noll T. G.
Published: August 2011

Abstract. The implementation of integrated circuits becomes more and more difficult in the Ultra-Deep-Submicron regime due to sub-wavelength lithography issues. An approach called Brick-Based Design was recently proposed to eliminate the disadvantages of staying with the classical approach to layout design. Prefix adders are a core component in a wide variety of applications due to their high speed and regular topology. In this paper, a modified prefix operator for prefix adders is proposed which is well suited for brick-style layout implementation and, in addition, offers an increase in efficiency. The proposed operator makes it possible to use a mirror gate for the generation of both generate and propagate signals, which exhibits a forbidden input signal combination. This "forbidden state" causes an increase in power dissipation due to transient short circuit currents. The effect of the forbidden state was quantified as part of a comparison against the classical prefix operator, based on 64-bit Sklansky adders implemented in a 40-nm CMOS technology. The effects of the forbidden state were found to be well acceptable. The implementation of the adder based on the proposed prefix operator reduces the area by 29% while increasing the power by 13% compared to one based on the classical operator.
Betrachtungen zur Frequenzplanung für terrestrisches Fernsehen in den 50er Jahren in Mitteleuropa
Authors: Kühn U.
Published: August 2011

Abstract. Der Bericht beleuchtet die Entwicklung der Fernseh- und Rundfunknetze im Osten Deutschlands ab Anfang der 50er Jahre. Neben einer ausführlichen Darstellung der technischen Aspekte liegt ein weiterer Schwerpunkt auf der Darstellung der nötigen Zusammenarbeit mit den Arbeitsgruppen der angrenzenden Länder. Diese war, bedingt durch die politische Lage, gerade mit den Experten aus Westdeutschland oft schwierig. Die maßgeblich beteiligten Personen und ihre Arbeiten werden vorgestellt. Der Autor war in leitender Position an der Entwicklung in Ostdeutschland beteiligt und liefert mit diesem Bericht einen aus technischer und historischer Sicht wertvollen Beitrag zur Entwicklung des Rundfunks.
Motion compensation of short-range, wide-beam synthetic aperture radar
Authors: Reichthalhammer T. , Biebl E.
Published: August 2011

Abstract. Up to now, SAR systems are a well known possibility for long-range detection. Applying them for short-range applications with wide-beam antennas, of course, does not increase the resolution but the probability to detect hidden targets with an anisotropic radar cross section significantly in comparison to other detection systems. Working with an appropriate wavelength even improves the possiblity to look through natural cover like grass. An application is detecting fawn while pasture mowing. The main issue in such applications is the antenna's motion in range direction as it is carried by cars or traction engines. If motion is not compensated, the phase cannot be reconstructed correctly, the resolution gets poorer and, in worst case, the target even disappears. Conventional methods for motion compensation either fail for wide beam antennas, since for contributions of wide angles the phase reconstruction is incorrect, or is not applicable for realtime data processing, because the processing time due to interpolation or similar steps is very high. We present a method of image reconstruction regarding motion of the antenna as well as wide beamwidth. This method is analyzed concerning processing time in comparison to the conventional image reconstruction. In our system we use a combination of algorithms. There is shown a comparison for different algorithms dependent of the antenna's motion and aperture angle.
Suppression of grating lobes for MMW sparse array setups
Authors: Bertl S. , Kirschner A. , Detlefsen J.
Published: August 2011

Abstract. For arrays the placement of the single elements determines the angular resolution and the unambiguity interval. The width of the total array determines the resolution capabilities. The wider the elements are placed from each other, the more space in Fourier domain is covered by the measurement and the resolution in time domain will improve. On the other hand the density of the elements has an effect on the angular interval in which objects can be detected unambiguously. For objects within the unambiguous interval grating lobes will appear outside this area while objects outside result in grating lobes in the interval of interest. In this paper the properties of arrays regarding resolution and unambiguity interval will be discussed and methods for the suppression of ambiguous grating lobes are suggested. One approach to suppress the influence of the grating lobes lies in the evaluation of different frequency bands.
Design and analysis of an isotropic two-dimensional planar Composite Right/Left-Handed waveguide structure
Authors: Eberspächer M. A. , Bauer M. , Eibert T. F.
Published: August 2011

Abstract. A two-dimensional isotropic Composite Right/Left-Handed (CRLH) waveguide structure is proposed which is designed for operation in X-band. The balanced structure possesses left-handed behaviour over a large bandwidth from 7.5 GHz up to its transition frequency at 10 GHz. Above this region, the unit cell behaves in a right-handed manner up to 13.5 GHz. Operating the structure within these bands yields a frequency dependent index of refraction ranging from −2.5 ≤ n ≤ 0.8. Isotropic characteristics are obtained between 8.5 GHz ≤ f ≤ 12 GHz resulting in −1.5 ≤ n ≤ 0.8. The planar CRLH structure is designed based on transmission line theory, implemented in microstrip technology and optimized using full-wave simulation software. An equivalent circuit model is determined describing the electromagnetic behaviour of the structure whose element values are obtained by even and odd mode analysis. The design of the unit cell requires an appropriate de-embedding process in order to enable an analysis in terms of dispersion characteristics and Bloch impedance, which are performed both.
Application of CMAQ at a hemispheric scale for atmospheric mercury simulations
Authors: Pongprueksa P. , Lin C. J. , Singhasuk P. , Pan L. , Ho T. C. , Chu H. W.
Published: August 2011

Abstract. Application of a regional model to study of fate and transport of a global pollutant such as mercury in the atmosphere can be challenging and improper usage of models may lead to questionable results. The difficulties in such application stem from the fact that regional models are usually used in relatively small domains and rely heavily on initial and boundary conditions (IC/BC) provided by global models where atmospheric physics and chemical mechanisms are generally diverse. This problem is particularly apparent for a persistent air pollutant such as mercury. In this study, a conventional application of the CMAQ (Community Multi-scale Air Quality) modeling system on regional scale was extended towards a hemispheric scale. Two simulations were performed using different IC/BC obtained from two global models. In terms of model evaluation, aircraft measurements of total gaseous mercury (TGM) concentration as well as mercury concentration and deposition data from ground-based measurements were used altogether in comparisons with the model simulations. The model results suggested an improvement in performance, as evidenced by a better circulation of the pollutant in Northern hemisphere relative to regional-scale simulations performed in our previous work. In this study, the simulation results using the two different inputs were found to be convergent as the simulation time progressed. The model results also suggested that BC has much weaker influence on the simulation results in a hemispheric domain than that on our previous regional assessment where BC was found to be one of the most important factors. In addition, mitigations of influences from IC/BC on model results in a hemispheric domain and implication of peaks of TGM concentration evident in aircraft measurement are also discussed.
Impact of Brand Diversification on Firm Performance: A Study of Restaurant Firms
Authors: Choi Kyuwan , Kang Kyung Ho , Lee Seoki , Lee Kyuseok
Published: August 2011

In spite of varying brand portfolio strategies employed by restaurant firms in response to the constant growth of the restaurant industry, research on the effect of brand diversification on the performance of restaurant firms has been rare. This study examines the impact of the degree of brand diversification among sampled publicly traded US restaurants. The results show a consistent, significant and negative effect from the degree of brand diversification on the performance of the sampled restaurant firms. The authors' investigation suggests that restaurant managers, when implementing a brand diversification strategy, should consider the firm's scale, sales efficiency, general and administrative expenses, franchising strategy and positioning of brands.
Tourism Destination Competitiveness: Second Thoughts on the World Economic Forum Reports
Authors: Mazanec Josef A. , Ring Amata
Published: August 2011

The Travel and Tourism Competitiveness Reports of the World Economic Forum elaborate the Travel and Tourism Competitiveness Index (TTCI) as an overall measure of destination competitiveness for 130 economies worldwide. From a tourism management point of view, a measure such as the TTCI is expected to be instrumental in explaining and predicting the tourism performance of receiving countries. This study explores several ways to transform the TTCI into a formative structural model. Partial least squares path modelling, PLS regression, mixture modelling and non-linear covariance-based structural equation modelling are applied to examine the TTCI's predictive power. The analysis probes possible measures for improvement. The destination countries may be subject to unobserved heterogeneity with regard to how the various constituents of competitiveness act on tourism performance. Interaction phenomena seem to prohibit a simple cause–effect pattern and non-linear relationships show encouraging results.
Research Note: Re-Examining the Tourism-Led Growth Hypothesis for Turkey
Authors: Husein Jamal , Kara S. Murat
Published: August 2011

Since the 1980s, Turkey has given priority to the advancement and expansion of its tourism industry as part of achieving economic growth and development. This study empirically re-examines the possible causal relationships among tourism receipts, real exchange rate and economic growth by using annual data (1964–2006). Johansen multivariate cointegration analysis reveals the existence of a ‘stable’ and significant long-run equilibrium relationship among real GDP, tourism receipts and real exchange rate (RER). Granger causality tests based on the error correction model indicate a unidirectional causality from tourism receipts and RER to real GDP.
Isolation of Human B Cell Populations
Authors: Heine Guido , Sims Gary P. , Worm Margitta , Lipsky Peter E. , Radbruch Andreas
Published: August 2011

To study the function and biology of human B cells, it is necessary to isolate pure populations. Historically, B cells were enriched by the sequential depletion of monocytes, natural killer cells, and T cells. However, this time‐consuming process has been superseded by sorting methods using specific antibodies, targeting, in negative‐selection strategies, unwanted cell types, or, in positive‐selection strategies, B cell markers such as CD19. Here we describe in detail four methods for isolating B cells from human blood or mononuclear cells, and discuss how these techniques can be combined with fluorescent cell sorting for the characterization of specific B cell populations. Curr. Protoc. Immunol. 94:7.5.1‐7.5.14. © 2011 by John Wiley & Sons, Inc.
A Micromachined Reconfigurable Metamaterial via Reconfiguration of Asymmetric Split‐Ring Resonators
Authors: Fu Yuan Hsing , Liu Ai Qun , Zhu Wei Ming , Zhang Xu Ming , Tsai Din Ping , Zhang Jing Bo , Mei Ting , Tao Ji Fang , Guo Hong Chen , Zhang Xin Hai , Teng Jing Hua , Zheludev Nikolay I. , Lo Guo Qiang , Kwong Dim Lee
Published: August 2011

A micromachined reconfigurable metamaterial is presented, whose unit cell consists of a pair of asymmetric split‐ring resonators (ASRRs); one is fixed to the substrate while the other is patterned on a movable frame. The reconfigurable metamaterial and the supporting structures (e.g., microactuators, anchors, supporting frames, etc.) are fabricated on a silicon‐on‐insulator wafer using deep reactive‐ion etching (DRIE). By adjusting the distance between the two ASRRs, the strength of dipole–dipole coupling can be tuned continuously using the micromachined actuators and this enables tailoring of the electromagnetic response. The reconfiguration of unit cells endows the micromachined reconfigurable metamaterials with unique merits such as electromagnetic response under normal incidence and wide tuning of resonant frequency (measured as 31% and 22% for transverse electric polarization and transverse magnetic polarization, respectively). The reconfiguration could also allow switching between the polarization‐dependent and polarization‐independent states. With these features, the micromachined reconfigurable metamaterials may find potential applications in transformation optics devices, sensors, intelligent detectors, tunable frequency‐selective surfaces, and spectral filters.
Self‐Healing Fibre Reinforced Composites via a Bioinspired Vasculature
Authors: Norris Christopher J. , Meadway Gregory J. , O'Sullivan Michael J. , Bond Ian P. , Trask Richard S.
Published: August 2011

This paper demonstrates the first steps towards self‐healing composites that exploit a design philosophy inspired by the damage tolerance and self‐repair functions of bone. Cracking in either fibre reinforced polymers (FRP) or bone, if left unattended, can grow under subsequent cyclic stresses eventually leading to catastrophic failure of the structure. On detection of cracks, an FRP component must be repaired or completely replaced, whereas bone utilises a series of complex processes to repair such damage. Under normal circumstances, these processes allow the skeleton to continually perform over the lifespan of the organism, a highly desirable aspiration for engineering materials. A simple vasculature design incorporated into a FRP via a “lost wax” process was found to facilitate a self‐healing function which resulted in an outstanding recovery (≥96%) in post‐impact compression strength. The process involved infusion of a healing resin through the vascule channels. Resin egress from the backface damage, ultrasonic C‐scan testing, and microscopic evaluation all provide evidence that sufficient vascule–damage connectivity exists to confer a reliable and efficient self‐healing function.
Polyspecific associations between squirrel monkeys (Saimiri sciureus) and other primates in eastern Amazonia
Authors: Pinheiro Tatyana , Ferrari Stephen F. , Lopes Maria Aparecida
Published: August 2011

One of the most common types of polyspecific association observed in Neotropical primate communities is that between squirrel monkeys (Saimiri) and capuchins (Cebus). The present study focused on association patterns in two Saimiri sciureus groups in eastern Brazilian Amazonia, between March and October, 2009. The associations were analyzed in terms of the species involved, the degree of association, and niche breadth and overlap. The study involved two S. sciureus groups (B4 and GI) on the right and left bank of the Tocantins River, respectively, within the area of the Tucuruí reservoir in southeastern Pará. Relations between species were classified as associations (individuals within 50 m and moving in the same direction), and encounters (individuals within 50 m and no coordinated movement). Group B4 was in association with Cebus apella during 100% of monitoring, and with Chiropotes satanas in 20.2%. By contrast, Group GI associated with Cebus 54.8% of the time, and with Chiropotes utahickae 2.5%. Encounters with Alouatta belzebul and Saguinus niger were recorded at both sites, with Aotus azarae and Dasyprocta prymnolopha at B4, and with Callicebus moloch, Dasyproct aleporina, Mazama gouazoubira, and Nasua nasua at GI. Overall, Saimiri had a broader niche than Cebus in terms of vertical spacing and diet, but not for substrate use. This pattern did not appear to be affected by association. While group GI spent significantly (P<0.05) more time in association with Cebus during the wet season, group B4 associated with Chiropotes more during the dry season. Despite the higher association rates, niche overlap was greater for all variables at B4. This may reflect differences in the ranging and foraging patterns at the two sites, and the varying potential benefits of association for Saimiri. Am. J. Primatol. 73:1145–1151, 2011. © 2011 Wiley Periodicals, Inc.
Fetal Lung Epithelial Ion Channels Relocate in the Cell Membrane During Late Gestation
Authors: Beard Lamonta L. , Li Tianbo , Hu Yang , Folkesson Hans G.
Published: August 2011

Near the end of gestation, the direction of ion and fluid flow across the alveolar epithelium rapidly changes from secretion to absorption. Thus, the relative cell membrane location of epithelial Na channels (ENaCs) and cystic fibrosis transmembrane regulator (CFTR) Cl channels during late fetal lung development and after maternal interleukin‐1β (IL‐1β) pretreatment was the focus of our study. Western blot analysis after sucrose gradient separation of caveolin‐1‐(Cav‐1)‐rich membrane regions (CRR) and Cav‐1‐poor membrane (non‐CRR) revealed primary CRR ENaC localization at gestation day (GD) 61 in guinea pigs. Correlating with the natural induction of distal lung fluid absorption, ENaC appeared in the non‐CRR cell membrane regions at GD68. Conversely, CFTR was present in the non‐CRR cell membrane regions at GD61 and in the CRRs at GD68. IL‐1β‐induced conversion to distal lung fluid absorption at GD61 was associated with ENaC non‐CRR presence and CFTR CRR presence, suggesting that relative ENaC and CFTR locations induced distal lung fluid absorption and decreased fluid secretion. Instilling fetal lungs with the CRR‐disrupting agent methyl‐β‐cyclodextrin resulted in the conversion from lung fluid secretion to absorption and ENaC non‐CRR presence at GD61. Coimmunoprecipitation of Cav‐1 with α‐ and β‐ENaC demonstrated reduced coimmunoprecipitation with increased GD and after IL‐1β pretreatment. On the other hand, coimmunoprecipitation of Cav‐1 with CFTR demonstrated increased coimmunoprecipitation with increasing GD and after IL‐1β pretreatment. This concept may provide novel molecular mechanisms for the rapid transition from fetal distal lung fluid secretion to absorption in near‐term lungs. Anat Rec, 2011. © 2011 Wiley‐Liss, Inc.
Functional Anatomy and Adaptation of Male Gorillas (Gorilla gorilla gorilla) With Comparison to Male Orangutans (Pongo pygmaeus)
Authors: Zihlman Adrienne L. , Mcfarland Robin K. , Underwood Carol E.
Published: August 2011

Great apes diversified during the Miocene in Old World forests. Two lineages, gorillas in Africa and orangutans in Asia, have sexual dimorphisms of super‐sized males, though they presumably diverged from a smaller common ancestor. We test the hypothesis that they increased in body mass independently and convergently, and that their many postcranial differences reflect locomotor differences. Whole body dissections of five adult male gorillas and four adult male orangutans allowed quantification of body mass distribution to limb segments, of body composition (muscle, bone, skin, and fat relative to total body mass), and of muscle distribution and proportions. Results demonstrate that gorilla forelimb anatomy accommodates shoulder joint mobility for vertical climbing and reaching while maintaining joint stability during quadrupedal locomotion. The heavily muscled hind limbs are equipped for propulsion and weight‐bearing over relatively stable substrates on the forest floor. In contrast, orangutan forelimb length, muscle mass, and joint construction are modified for strength and mobility in climbing, bridging, and traveling over flexible supports through the forest canopy. Muscles of hip, knee, and ankle joints provide rotational and prehensile strength essential for moving on unstable and discontinuous branches. We conclude that anatomical similarities are due to common ancestry and that differences in postcranial anatomy reflect powerful selection for divergent locomotor adaptations. These data further support the evolutionary conclusion that gorillas fall with chimpanzees and humans as part of the African hominoid radiation; orangutans are a specialized outlier. Anat Rec, 2011. © 2011 Wiley‐Liss, Inc.
Ferrocene‐Functionalized Disubstituted Polyacetylenes with High Light Refractivity: Synthesis through Polymer Reaction by Using Click Chemistry and Application as Precursors to Magnetic Nanoparticles
Authors: Jim Cathy K. W. , Qin Anjun , Mahtab Faisal , Lam Jacky W. Y. , Tang Ben Zhong
Published: August 2011

Ferrocene‐functionalized disubstituted polyacetylenes are synthesized in high yields by copper‐catalyzed click reactions of azido‐decorated poly(1‐phenyl‐1‐hexyne) and poly(diphenylacetylene) with 1‐ethynylferrocene. All the organometallic polymers are soluble and film‐forming. They enjoy high thermal stability (≥300 °C) and are redox‐active. Thanks to the ferrocenyl units, thin films of the polymers show high refractive indices (n=1.745–1.698) in the wavelength region of 400–1700 nm as well as high Abbé numbers (vD’ up to 426) and low optical dispersions (D’ down to 0.002) at telecommunication important wavelengths. Pyrolyses of the polymers under nitrogen furnish magnetic ceramics with high magnetizabilities.
Robust Stability and Stabilization Criteria for Discrete Singular Time‐Delay LPV Systems
Authors: Zhang Xian , Zhu Huanyu
Published: August 2011

This paper is concerned with establishing robust stability and stabilization criteria for discrete singular time‐delay linear parameter varying (LPV) systems. Firstly, a robust stability criterion is obtained for this class of systems by a delay‐partition approach, and thereby a less conservative sufficient condition which guarantees discrete singular time‐delay LPV systems to be admissible is given. Secondly, a class of state feedback controllers for stabilizing discrete singular time‐delay LPV systems is designed. Finally, compared with existing results, the numerical results of several examples illustrate the effectiveness of the approach proposed in this paper.

Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
Einfluss der Verbundtragwirkung bei mehrschichtigen Stahlbetonwandtafeln mit innen liegender Wärmedämmung
Authors: Pahn Matthias , Schnell Jürgen
Published: August 2011

Für mehrschichtige Stahlbetonwandtafeln mit Verbindungsmitteln aus glasfaserverstärktem Kunststoff (GFK) sind neben den Nachweisen zur Tragfähigkeit auch Nachweise im Grenzzustand der Gebrauchstauglichkeit zu führen. Insbesondere bei hohen, schlanken Wandelementen ist das Verbundtragverhalten unter Einbeziehung der innen liegenden Wärmedämmschicht dieser Bauteile zu berücksichtigen. Basierend auf dem gekoppelten Differentialgleichungssystem der Sandwichtheorie werden analytische, geschlossene Lösungen zur Berechnung der Schnittund Verformungsgrößen des Fassadensystems vorgestellt. Im Rahmen von Bauteilversuchen wird die Verbundtragwirkung an mehrschichtigen Stahlbetonplattenstreifen überprüft, und es erfolgt die Verifizierung des Berechnungsmodells anhand der gemessenen Bauteildurchbiegung und der Relativverschiebung zwischen den Schalen. Eine Parameterstudie gibt Aufschluss darüber, inwieweit die Zustandsgrößen aus der Verbundtragwirkung bei den Nachweisen im Grenzzustand der Gebrauchstauglichkeit berücksichtigt werden müssen.

Effects of composite action on multilayered sandwich panels with integrated insulation

Prefabricated multilayered concrete walls with integrated insulation and fastened with connectors of glass‐fiber reinforced polymers have to be designed to sustain ultimate limit state and serviceability state. Especially, high and slender wall panels are influenced by the composite action between the concrete layers and the integrated insulation. Solving the coupled system of differential equations of the sandwich theory analytically, closed solutions to calculate deformations and internal forces of the façade system will be shown. An experimental study shows the effect of composite action at multilayered sandwich panels. A verification of the calculation model is obtained by comparing the measured mid‐span deflection of the concrete member to the relative deformation between the concrete layers. A parameter study shows the influence of internal forces and deformations due to the composite action at serviceability state.
Optimal weight in estimating and comparing areas under the receiver operating characteristic curve using longitudinal data
Authors: Wu Yougui , Wang Xiaofei
Published: August 2011

In the setting of longitudinal study, subjects are followed for the occurrence of some dichotomous outcome. In many of these studies, some markers are also obtained repeatedly during the study period. Emir et al. introduced a non‐parametric approach to the estimation of the area under the ROC curve of a repeated marker. Their non‐parametric estimate involves assigning a weight to each subject. There are two weighting schemes suggested in their paper: one for the case when within‐patient correlation is low, and the other for the case when within‐subject correlation is high. However, it is not clear how to assign weights to marker measurements when within‐patient correlation is modest. In this paper, we consider the optimal weights that minimize the variance of the estimate of the area under the ROC curve (AUC) of a repeated marker, as well as the optimal weights that minimize the variance of the AUC difference between two repeated markers. Our results in this paper show that the optimal weights depend not only on the within‐patient control–case correlation in the longitudinal data, but also on the proportion of subjects that become cases. More importantly, we show that the loss of efficiency by using the two weighting schemes suggested by Emir et al. instead of our optimal weights can be severe when there is a large within‐subject control–case correlation and the proportion of subjects that become cases is small, which is often the case in longitudinal study settings.
Cross‐linked collagen sponges loaded with plant polyphenols with inhibitory activity towards chronic wound enzymes
Authors: Antonio Francesko , Guillem Rocasalbas , Sonia Touriño , Clara Mattu , Piergiorgio Gentile , Valeria Chiono , Gianluca Ciardelli , Tzanov Tzanko
Published: August 2011

Collagen sponges loaded with polyphenols from Hamamelis virginiana were investigated as active materials for chronic wound dressings, evaluating in vitro the inhibition of two major enzymes that impair the wound healing process – myeloperoxidase (MPO) and collagenase. Prior to polyphenols loading, collagen was cross‐linked with genipin to improve its biostability. The effect of genipin cross‐linking and polyphenol concentration in the development of mechanically and enzymatically stable sponges was studied. The tensile strength of the cross‐linked collagen increased with the increase of the cross‐linking degree, coupled to decrease in the elongation and the swelling capacity of the sponges. The stability of the sponges to collagenase digestion reached maximum when 1 mM genipin was used. However, the biostability decreased more than 10‐fold after loading the sponges with polyphenols (0.5 mg/mL), nevertheless, this effect was partially overcome using higher concentration of polyphenols (1 and 2 mg/mL) to inhibit collagenase. Moreover, the polyphenols released from the sponges were sufficient for complete inhibition of MPO activity. No considerable cytotoxicity of the genipin cross‐linked collagen loaded with polyphenols was observed evaluating the NIH 3T3 fibroblasts viability.
Tolerance of β‐diketone hydrolases as representatives of the crotonase superfamily towards organic solvents
Authors: Siirola Elina , Grischek Barbara , Clay Dorina , Frank Annika , Grogan Gideon , Kroutil Wolfgang
Published: August 2011

Crotonase superfamily enzymes catalyze a wide variety of reactions, including hydrolytic C–C bond cleavage in symmetrical β‐diketones by 6‐oxo camphor hydrolase (OCH) from Rhodococcus sp. The organic solvent tolerance and temperature stability of OCH and its structurally related ortholog Anabaena β‐diketone hydrolase have been investigated. Both enzymes showed excellent tolerance toward organic solvents; for instance, even in the presence of 80% (v/v) THF or dioxane, OCH was still active. In most solvent mixtures, except methanol, the stereospecificity was conserved (>99% e.e. of product), hence neither the type of solvent nor its concentration appeared to have an effect on the stereoselectivity of the enzyme. Attempts to correlate the observed activities with log P, functional solvent group or denaturing capacity (DC) of the solvent were only successful in the case of DC for water miscible solvents. This study represents the first investigation of organic solvent stability for members of the crotonase superfamily. Biotechnol. Bioeng. 2011;108: 2815–2822. © 2011 Wiley Periodicals, Inc.
Elucidating the effects of laccase‐modifying compounds treatments on bast and core fibers in flax pulp
Authors: Fillat Amanda , Roncero M. Blanca , Vidal Teresa
Published: August 2011

Laccases in combination with various chemical compounds have been tested with a view to obtain environmental friendly, high‐value paper products from unbleached flax pulp, which is currently being assessed as a raw material for biotechnological innovation. With the aim of better understanding the effects of violuric acid (VA) and p‐coumaric acid (PCA) on flax pulp, changes in the chemical composition of the two major fiber types it contains were assessed. Following classification, the initial pulp was split into two fractions according to fiber size, namely: bast (long) fibers and core (short) fibers. Fiber size was found to significantly influence the properties of pulp and it response to various laccase treatments. The laccase‐PCA treatment substantially increased kappa number (KN) and color in both fiber fractions, which suggests grafting of the phenolic compound onto fibers. On the other hand, the laccase‐VA treatment produced long fibers with a low lignin content (KN = 1.3) and a high brightness (5% points higher than for the control fraction), which testifies to its bleaching efficiency. Both biotreatments produced long fibers containing highly crystalline cellulose and caused HexA removal from global and short fibers. On the other hand, the laccase treatments caused no morphological changes in the fibers, the integrity of which was largely preserved. As shown here, laccase acts as polymerization agent with PCA and as delignification agent with VA; also, the two enzymes systems act differently on bast and core fibers. Biotechnol. Bioeng. 2012;109: 225–233. © 2011 Wiley Periodicals, Inc.