bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of silicon nanowire etching on signal‐to‐noise ratio of SiNW FETs for (bio)sensor applications
Authors: Moh T.S.Y. , Nie M. , Pandraud G. , de Smet L.C.P.M. , Sudhölter E.J.R. , Huang Q‐A. , Sarro P.M.
Published: July 2013

A high signal‐to‐noise ratio (SNR) in silicon nanowire (SiNW) field effect transistors (FETs) is crucial for detecting low concentrations of biological material as the signal changes are often small and difficult to be differentiated from the baseline signal. This reported work studies the low‐frequency noise (1/f) as in Hooge's constant, αH, and the device detection limit of the SiNW FETs to evaluate the influence of the etching process used to define the nanowires (NWs). Two etching methods are compared: plane‐dependent etching using potassium borate in water and reactive ion etching in Cl‐based chemistry. All investigated devices have similar dopant type, doping concentration and dimensions, and were fabricated with the same process flow with the exception of the NW definition. The extracted average Hooge's constant for wet etching is found to be at least an order of magnitude lower (αH, avg = 7.96 × 10−4) compared with dry plasma‐etched devices (αH, avg = 4.1 × 10−2), indicating a lower surface roughness and/or a lower amount of surface defects. This study shows that the newly developed method improves the electrical properties of the device, making it an interesting alternative to standard approaches used for fabrication of SiNW FETs as (bio)sensors.
High peak power pulses from dispersion optimised modelocked semiconductor laser
Authors: Balzer J.C. , Schlauch T. , Klehr A. , Erbert G. , Tränkle G. , Hofmann M.R.
Published: July 2013

Presented is an electrically pumped passively modelocked edge‐emitting semiconductor laser system in an external cavity setup with intracavity dispersion management. This concept, in combination with a pulse compressor, provides pulses as short as 158 fs. By expanding the setup with a tapered diode laser amplifier, peak powers up to 6.5 kW were achieved in the 850 nm wavelength range.
Effect of spark gap shape on time lag
Authors: Wan F. , Pommerenke D. , Shumiya H. , Araki K.
Published: July 2013

Presented is the effect of sharp spark gap on time lag, which is a very important factor in electrostatic discharge modelling. A long time lag induces a large discharge current and a fast rise time. The large discharge current often causes soft errors in many products. Through measurement and simulation, the relation between sharp edge and time lag is quantified. The result can be used in numerical simulation of breakdown voltage. With the numerical simulation, knowing only the geometry of the spark gap can obtain the discharge current.
Partwise bag‐of‐words‐based multi‐task learning for human action recognition
Authors: Liu An‐An , Su Yuting , Gao Zan , Hao Tong , Yang Zhao‐Xuan , Zhang Zhe
Published: July 2013

Proposed is a human action recognition method by partwise bag‐of‐words (BoW)‐based multi‐task learning. The authors present partwise BoW representation and furthermore formulate the action recognition task as a joint multi‐task learning problem by transfer learning penalised by a graph structure and sparsity to discover latent correlation and boost performances. A large‐scale experiment shows that this method can significantly improve performance over the standard BoW + SVM method. Moreover, the proposed method can achieve competing performances against the state‐of‐the‐art methods for human action recognition in an effective and easy to follow way.
1.4 GHz femtosecond comb generation by Fabry‐Pérot filtering of optical parametric oscillator frequency comb
Authors: Ferreiro T.I. , Lamour T.P. , Sun J. , Reid D.T.
Published: July 2013

Laser frequency combs based on optical parametric oscillators provide widely tunable sources of regularly spaced frequencies from the visible to the mid‐infrared, with potential applications in precision metrology, spectroscopy and astronomy. Reported is the extension of the comb mode spacing into the GHz domain by using a Fabry‐Pérot cavity, the length of which was electronically stabilised to a harmonic of the original pulse repetition frequency via a dither‐locking technique. A 1500 nm femtosecond optical parametric oscillator frequency comb, the repetition frequency and carrier‐envelope offset frequency of which were locked to 280 MHz and 10 MHz, respectively, was filtered by a high‐finesse cavity to generate a pulse sequence at 1.4 GHz, corresponding to a factor of five increase in the mode spacing of the comb.
Drivers’ willingness to engage with their mobile phone: the influence of phone function and road demand
Authors: Hancox Graham , Richardson John , Morris Andrew
Published: July 2013

Drivers normally elect whether or not to engage with a secondary task while driving. This study aimed to determine whether drivers’ willingness to engage with their mobile phone is affected by demands from the roadway environment and if these effects are more pronounced for some phone functions compared with others. Fifteen video clips were played to 20 participants representing different road scenarios, and therefore demands, such as driving on an empty auto route or turning right on a main arterial road. The participants then used three point Likert scales to rate their willingness to place or answer a call and send or read a text and a five point scale to rate the perceived riskiness of placing and answering a call only. Participants were also asked to think aloud when making their judgements so further insight could be gained. It was found that willingness to engage was affected by both the perceived roadway demands and the phone function under consideration. The perceived riskiness also affected willingness to engage when placing a call only. The think aloud element indicated the participants’ reasoning behind these findings as well as identifying possible future areas of research.
Impact of a combined accelerator–brake pedal solution on efficient driving
Authors: Schmitz Marcus , Maag Christian , Jagiellowicz Monika , Hanig Michael
Published: July 2013

The functionality of an electric vehicle enables to regenerate energy into the battery by using the electric motors for electric braking. By integrating this electric brake into the accelerator pedal, drivers are expected to use more often the electric brake and less often the hydraulic brake. However, the pedal system of a car is a crucial connection between driver and car. Any modification of this part can lead to decreasing acceptance. Two driving simulator studies were conducted to investigate the effect of three different settings of electric braking and the impact of a combined pedal solution (CPS) on acceptance and energy consumption. Participants performed test drives in rural and urban environments, with both the CPS and a conventional pedal solution and different levels of recuperation. The results show that drivers preferred stronger electric braking and the CPS (instead of a conventional pedal solution). With the CPS, drivers used less often the hydraulic brake and drove more efficiently.
Influence of highway three‐dimensional coordination on drivers’ perception of horizontal curvature and available sight distance
Authors: Moreno Ana Tsui , Garcia Alfredo , Camacho‐Torregrosa Francisco Javier , Llorca Carlos
Published: July 2013

Drivers' road perception is an important human factor of comfort and safety on driving. Available sight distance of crest vertical curves superimposed on horizontal curves can be geometrically optimised by applying 3D coordination criteria. However, drivers might not perceive available sight distance improvements. Two approaches were used to investigate the effect of geometrical optimised design on perceived sharpness and visibility of isolated crest vertical curves overlapped with horizontal curves. A survey‐based approach was used to evaluate subjective perception of 100 drivers. Three‐dimensional renderings were displayed to subjects; who were asked to rank the curves by sharpness and sight distance. Moreover, 50 of those drivers previously participated on a driving simulation experiment involving the same curves, so objective driving data were collected too. Drivers' survey results indicate that driver's curve perception depends on the algebraic difference of grades while coordination of vertical and horizontal curves does not appear to affect this perception. On the other hand, the operating speeds on different curves were not statistically different from each other. Surprisingly, the operating speeds on a flat curve tended to be lower than on the vertical crest curves superimposed on the same horizontal curve. Likely causes are discussed in the paper.
Identifying critical incidents in naturalistic driving data: experiences from a promoting real life observation for gaining understanding of road user behaviour in Europe small‐scale field trial
Authors: Tontsch Anita , Valero‐Mora Pedro Miguel , Pareja Ignacio
Published: July 2013

The methodology of naturalistic driving observation aspires to observe the driver and his environment while driving in natural driving settings. It is of great importance in research on road safety as this method of observing road users eliminates the disadvantages of traditional methods like simulator studies or interviews. However, it produces vast such amounts of data and challenges data reduction and data analysis. Therefore automatic methods for filtering critical incidents based on thresholds for numerical data are often applied to select the data to be analysed. This study reports a small‐scale field trial in Valencia, Spain, which was conducted within the promoting real life observation for gaining understanding of road user behaviour in Europe project. The analysis of the numerical data using thresholds resulted in a great number of false alarms and did not identify safety‐critical sequences. In contrast, video analysis revealed a number of critical events that had not been previously detected using the numerical parameters. The study conveyed the importance of continuous video recording in these kinds of studies and showed that the methodology of data reduction for naturalistic driving studies requires further development in order to be able to capture all the relevant incidents automatically.
Do drivers reduce their headway to a lead vehicle because of the presence of platoons in traffic? A conformity study conducted within a simulator
Authors: Gouy Magali , Diels Cyriel , Reed Nick , Stevens Alan , Burnett Gary
Published: July 2013

Electronically coupled platoons of vehicles have the potential to increase the efficiency of transport on unmodified motorways. In doing so, the time headway (THW) between participating vehicles will be dramatically reduced. The present study investigated whether drivers are willing to keep a THW smaller than their preferred one to conform to the norm established by the presence of platoons holding short THWs. Firstly, two constructs had to be distinguished to answer this question: the preferred THWs represent a range of THWs drivers feel safe with and the THW that is indeed adopted by drivers in a given situation (adopted THW). Secondly, comparing adopted and preferred THW informs about whether drivers would adopt a THW beyond their preferred one as a result of the influence of platoons. Forty‐two participants were asked to follow a lead vehicle (LV) in three different traffic conditions. In two conditions, there was a platoon of vehicles in the inside lane, where the THW between the vehicles was either large (THW = 1.0 s) or short (THW = 0.3 s). In a third baseline drive, the LV was the only vehicle present. Preferred THW was assessed after each traffic conditions with the psychophysical method of limits. Results show a consistency of preferred THW and there is a significant difference in adopted THW values throughout the conditions, which supports the idea of two distinct constructs. Further, participants’ minimum adopted THW did not drop under but was very close to the minimum preferred THW in condition THW03. It can be concluded that platoons could lead drivers to drive closer to their limits. Further studies need to investigate if in other conditions, drivers would go below their limit and in this case, consequences on the drivers (e.g. in terms of safety, workload and performance) will also require further investigations.
On small‐signal amplification of a TM circular cylindrical wave‐guide mode in a gyro‐TWT
Authors: Kalyanasundaram Natarajan , Saini Jasmine
Published: July 2013

A self‐consistent kinetic‐theory based method of analysing the small‐signal amplification of a transverse magnetic (TM) mode of a circular cylindrical waveguide linearly interacting with an annular beam of gyrating electrons in a gyro‐travelling wave tube (TWT) configuration is presented. When the cyclotron‐resonance condition is enforced over the entire frequency range by allowing the gyro‐radius and the relativistic factor to be frequency‐dependent for a constant value of the axial electron speed chosen to coincide with the reciprocal of the TM‐mode phase speed at a particular frequency, the initial growth rate of the interacting TM wave is seen to exhibits a shallow minimum close to, but shifted to the right of, that frequency. The growth‐rate curve, however, exhibits two maxima on either side of the minimum, a sharp but large maximum to the left and a broad but a smaller maximum to the right. A gyro‐TWT designed by choosing the amplifier parameters (none of them varying any longer with frequency) in such a way as to place the broad maximum of the growth‐rate curve at the design frequency is shown to be capable of operation over a wide band of frequencies around the design frequency coupled with a decent value of small‐signal gain and negligible frequency distortion.
Enhancing the security of communication via directly modulated antenna arrays
Authors: Shi HongZhe , Tennant Alan
Published: July 2013

A new approach to enhance the security of data transmission using direction dependent antenna modulation based on an array with wide element spacing combined with directional array elements is presented. For illustrative purposes, the system investigated, and reported here, consists of an array of only two elements but the approach is general and can be extended to multi‐element array systems. It is shown that by increasing the element spacing of an array the directional error rate characteristics of the system, in a given direction, can be significantly improved. Furthermore, the directly modulated system shows superior error rate performance to that of an equivalent, conventionally modulated, system in the grating lobe directions. The error rate characteristics of the proposed system are analysed for two scenarios: firstly when the angular separation between an eavesdropper and the intended recipient is small and secondly for the case when a potential eavesdropper is located much closer to the transmit antenna than the intended recipient.
Broadband design of a low‐profile reflector antenna
Authors: Tayebi Abdelhamid , Gómez Josefa , González Iván , Cátedra Felipe
Published: July 2013

This work presents the design and analysis of a modified Fresnel zone plate reflector for broadband operation. A new technology based on slight deformations on a flat metallic surface is applied to obtain the geometrical model of the proposed flat reflector antenna. In comparison with reflectarrays, Fresnel zone reflectors are lossless, low cost, easy to fabricate and broadband. According to the specifications of a previously published reflectarray, a centre‐fed prototype whose dimensions are 28 × 21 cm has been designed and analysed showing a maximum gain of 28.06 dBi at 12.5 GHz and a 32.8% 3 dB gain bandwidth in the range between 10.4 and 14.5 GHz. A second prototype has been designed and analysed to evaluate the performance of the proposed design method compared with a previous design of a Fresnel zone reflector. Better results in terms of gain and antenna efficiency have been obtained.
V‐band bandpass filter with continuously variable centre frequency
Authors: Psychogiou Dimitra , Peroulis Dimitrios , Li Yunjia , Hafner Christian
Published: July 2013

A second‐order bandpass filter (BPF) with continuously variable centre frequency tuning is presented in this article. Evanescent‐mode cavity resonators with variable capacitive loadings are used as tuning elements. Tuning is achieved by means of micro‐electromechanical‐systems (MEMS)‐actuated highly conductive rigid fingers that feature an out‐of‐plane deflection. For an applied DC bias voltage between 0 and 27.3 V the centre frequency of the BPF is tuned from 67.4 to 63.2 GHz (4.2 GHz). For this frequency band, the fractional bandwidth (FBW) varies between 8.3 and 3.4% and the in‐band insertion loss between 1.45 and 5 dB.
Compact negative‐epsilon stop‐band structures based on double‐layer chiral inclusions
Authors: Hashemi Seyed Mohammad , Soleimani Mohammad , Tretyakov Sergei A.
Published: July 2013

Here the authors propose to use electrically excited compact chiral resonators in microstrip configurations for realisation of weakly‐radiating stop‐band transmission lines. The fundamental resonant mode of these resonators can be excited by both electric and magnetic fields applied parallel to the spiral axis. The authors propose to use a racemic arrangement of an equal amount of left‐ and right‐handed chiral particles between the ground plane and the signal strip and orient the particles so that they are excited by the electric field of the microstrip line. The advantage of this configuration (in addition to strong coupling and weak radiation from excited particles) is that the ground plane can be preserved from being etched (continuous ground structure). The other advantage is that the size of negative permittivity lines loaded with chiral particles can be made very small compared to previous implementations based on complementary split‐ring resonators. The circuit models with properly extracted parameters accurately describe the behaviour of both negative permittivity and double‐negative lines loaded with electrically coupled resonators. This parameter extraction technique is based on the comparison between the simulated (or measured) transmission and reflection characteristics of the host line loaded with such resonators and those obtained from its lumped‐element equivalent circuit model.
Developing single‐layer ultra‐wideband band‐pass filter with multiple (triple and quadruple) notches
Authors: Nosrati Mehdi , Daneshmand Mojgan
Published: July 2013

New ultra‐wideband (UWB) band‐pass filters (BPFs) with multiple (triple and quadruple) notches are proposed. A systematic approach is demonstrated to establish one to four or more notch‐bands within the passband of a UWB BPF on a single‐layer substrate using µ‐strip technology, while avoiding the use of any via‐holes. The proposed filters are based on parallel integration of gap‐coupled microstrip resonators (GCMR) and two tri‐section stepped‐impedance resonators (TSSIR) to generate multiple notches. Two notches are produced by the use of TSSIR fundamental and first spurious resonance frequencies and the third and fourth notches are introduced by developing transmission zeros using additional integrated GCMR. Two samples of triple and quadruple notch‐band UWB filters are fabricated and tested. In comparison to the previous triple single‐layer notch‐band BPFs with via‐holes, the proposed single‐layer triple notch BPF offers a size reduction of around 52%. The authors have also expanded the concept and designed a new quadruple notch‐band UWB BPF. The proposed filter uses only a single layer and can be easily mass‐produced with low cost.
Innovation and Scaling of ICT for the Bottom-Of-The-Pyramid
Authors: Foster Chris , Heeks Richard
Published: July 2013

Scaling represents successful diffusion that ensures sizeable impact and earnings from information and communication technology (ICT) innovations in emerging markets. Practice can still be shaped by dualistic views - innovation vs diffusion, pilot vs scale-up, lead firm vs other actors, technical vs social. Synthesising the literature that challenges these dualities, this paper creates a systemic perspective that is particularly appropriate for scaling of ICT to bottom-of-the-pyramid (BoP) markets. That perspective is then instantiated through the case study of a successfully-scaled ICT innovation that has reached millions of poor consumers: the Kenyan m-money system, M-Pesa. It finds that scaling of this ICT system can be understood as a four-stage process of exploratory, incremental then aggressive growth, followed by (attempted) standardisation. Throughout these stages of scaling, ongoing adaptive innovations have been fundamental and have been both necessitated and shaped by the BoP context. These innovations have been more socio-technical than technical, and have emerged from a growing variety of actors and locations closer to poor consumers than the lead firm. The lead firm has buffered the unfamiliarity of BoP markets by approaching them through the ‘middle-of-the-pyramid’ and by intensive learning. At times, its planned ‘shifts’ in scaling strategy have triggered adaptive innovations. At other times, emergent innovations and learning lead to incremental ‘drifts’ in lead firm strategy. ICT firms wishing to scale goods and services for BoP markets must therefore recognise the multi-locational, continuous, and emergent nature of innovation, and develop processes to monitor and address those innovations.
ICT Innovation in Emerging Economies: A Review of the Existing Literature and a Framework for Future Research
Authors: Xiao Xiao , Califf Christopher B , Sarker Saonee , Sarker Suprateek
Published: July 2013

ICT innovation is known to significantly elevate a country's growth and to enhance productivity. It is now well-acknowledged that emerging economies are beginning to innovate at a rapid rate despite some of the challenges they face. Given that these countries with such economies now comprise a third of the world's largest 25 economies, and that they are likely to be critical for the success of a global economy, it is important to understand how these economies innovate, what factors affect innovation in such nations, and what are the impacts. However, to the best of our knowledge, little research till date has been conducted on this topic, and the few existing studies have failed to catch the attention of the mainstream IS research community. We believe that the absence of studies is primarily due to a lack of understanding of what has been found with respect to ICT innovation in emerging economies, what needs to be studied, and how they should be studied. We attempt to contribute in this area by: (1) providing a comprehensive framework of existing research on ICT innovation in emerging economies, (2) highlighting the gaps that have been left behind, and (3) providing specific guidelines to future researchers, including a research model summarizing the salient issues that need examination. We believe that our study makes an important contribution to research on ICT innovation in emerging economies, and can be a useful resource for future researchers interested in this topic.
Dynamics of ligand exchange mechanism at Cu(II) in water: An ab initio quantum mechanical charge field molecular dynamics study with extended quantum mechanical region
Authors: Moin Syed Tarique , Hofer Thomas S. , Weiss Alexander K. H. , Rode Bernd M.
Published: July 2013

Ab initio quantum mechanical charge field molecular dynamics (QMCF-MD) were successfully applied to Cu(II) embedded in water to elucidate structure and to understand dynamics of ligand exchange mechanism. From the simulation studies, it was found that using an extended large quantum mechanical region including two shells of hydration is required for a better description of the dynamics of exchanging water molecules. The structural features characterized by radial distribution function, angular distribution function and other analytical parameters were consistent with experimental data. The major outcome of this study was the dynamics of exchange mechanism and reactions in the first hydration shell that could not be studied so far. The dynamical data such as mean residence time of the first shell water molecules and other relevant data from the simulations are close to the results determined experimentally. Another major characteristic of hydrated Cu(II) is the Jahn-Teller distortion which was also successfully reproduced, leading to the final conclusion that the dominating aqua complex is a 6-coordinated species. The ab initio QMCF-MD formalism proved again its capabilities of unraveling even ambiguous properties of hydrated species that are far difficult to explore by any conventional quantum mechanics/molecular mechanics (QM/MM) approach or experiment.
A quantum description of radiation damping and the free induction signal in magnetic resonance
Authors: Tropp James
Published: July 2013

We apply the methods of cavity quantum electrodynamics (CQED), to obtain a microscopic and fully quantum-mechanical picture of radiation damping in magnetic resonance, and the nascent formation of the free induction signal. Numerical solution of the Tavis-Cummings model – i.e., multiple spins 1/2 coupled to a lossless single-mode cavity – shows in fine detail the transfer of Zeeman energy, via spin coherence, to excite the cavity – represented here by a quantized LC resonator. The case of a single spin is also solved analytically. Although the motion of the Bloch vector is non-classical, we nonetheless show that the quantum mechanical Rabi nutation frequency (as enhanced by cavity coupling and stimulated emission) gives realistic estimates of macroscopic signal strength and the radiation damping constant in nuclear magnetic resonance. We also show how to introduce dissipation: cavity losses by means of a master equation, and relaxation by the phenomenological method of Bloch. The failure to obtain the full Bloch equations (unless semi-classical conditions are imposed on the cavity) is discussed in light of similar issues arising in CQED (and in earlier work in magnetic resonance as well), as are certain problems relative to quantization of the electromagnetic near-field.
Reduction of interfacial SiO2 at HfO2/Si interface with Ta2O5 cap
Authors: Kobashi Kazuyoshi , Nagata Takahiro , Ogura Atsushi , Nabatame Toshihide , Chikyow Toyohiro
Published: July 2013

We investigated SiO2 interfacial layer (IL-SiO2) reduction with a Ta2O5 cap to realize the direct contact formation of HfO2 on a Si substrate for the equivalent oxide thickness scaling of Hf-based high-k gate dielectrics. X-ray reflectivity and x-ray photoelectron spectroscopy measurements revealed that the Ta2O5 cap was effective in taking oxygen from the IL-SiO2 and caused SiO2 reduction, which resulted from Ta diffusion into the HfO2 layer from the Ta2O5. With this technique, the Ta2O5 cap deposited on the HfO2/SiO2/Si reduced the IL-SiO2 by 0.2 nm without any thermal treatment. Rapid thermal annealing at 300 °C enhanced the IL-SiO2 reduction. This result reveals that our method is a promising approach to achieve direct contact between the high-k layer and the Si substrate. Therefore, Ta2O5 has good potential as a cap for SiO2 interfacial layer reduction.
Ab initio determination of potential energy surfaces for the first two UV absorption bands of SO2
Authors: Xie Changjian , Hu Xixi , Zhou Linsen , Xie Daiqian , Guo Hua
Published: July 2013

Three-dimensional potential energy surfaces for the two lowest singlet ($\tilde A{}^1B_1 $Ã1B1 and $\tilde B{}^1A_2 $B̃1A2) and two lowest triplet ($\tilde a^3 B_1 $ã3B1 and $\tilde b^3 A_2 $b̃3A2) states of SO2 have been determined at the Davidson corrected internally contracted multi-reference configuration interaction level with the augmented correlation-consistent polarized triple-zeta basis set (icMRCI+Q/AVTZ). The non-adiabatically coupled singlet states, which are responsible for the complex Clements bands of the B band, are expressed in a 2 × 2 quasi-diabatic representation. The triplet state potential energy surfaces, which are responsible for the weak A band, were constructed in the adiabatic representation. The absorption spectrum spanning both the A and B bands, which is calculated with a three-state non-adiabatic coupled Hamiltonian, is in good agreement with experiment, thus validating the potential energy surfaces and their couplings.
Improved controlled atmosphere high temperature scanning probe microscope
Authors: Hansen K. V. , Wu Y. , Jacobsen T. , Mogensen M. B. , Theil Kuhn L.
Published: July 2013

To locally access electrochemical active surfaces and interfaces in operando at the sub-micron scale at high temperatures in a reactive gas atmosphere is of great importance to understand the basic mechanisms in new functional materials, for instance, for energy technologies, such as solid oxide fuel cells and electrolyzer cells. Here, we report on advanced improvements of our original controlled atmosphere high temperature scanning probe microscope, CAHT-SPM. The new microscope can employ a broad range of the scanning probe techniques including tapping mode, scanning tunneling microscopy, scanning tunneling spectroscopy, conductive atomic force microscopy, and Kelvin probe force microscopy. The temperature of the sample can be as high as 850 °C. Both reducing and oxidizing gases such as oxygen, hydrogen, and nitrogen can be added in the sample chamber and the oxygen partial pressure (pO2) is monitored by an oxygen sensor. We present here some examples of its capabilities demonstrated by high temperature topography with simultaneously ac electrical conductance measurements during atmosphere changes, electrochemical impedance spectroscopy at various temperatures, and measurements of the surface potential. The improved CAHT-SPM, therefore, holds a great potential for local sub-micron analysis of high-temperature and gas induced changes of a wide range of materials.
Coupled potential energy surface for the F(2P) + CH4 → HF + CH3 entrance channel and quantum dynamics of the CH4 · F− photodetachment
Authors: Westermann Till , Eisfeld Wolfgang , Manthe Uwe
Published: July 2013

An approach to construct vibronically and spin-orbit coupled diabatic potential energy surfaces (PESs) which describe all three relevant electronic states in the entrance channels of the X(P) + CH4 →HX + CH3 reactions (with X=F(2P), Cl(2P), or O(3P)) is introduced. The diabatization relies on the permutational symmetry present in the methane molecule and results in diabatic states which transform as the three p orbitals of the X atom. Spin-orbit coupling is easily and accurately included using the atomic spin-orbit coupling matrix of the isolated X atom. The method is applied to the F + CH4 system obtaining an accurate PES for the entrance channel based on ab initio multi-reference configuration interaction (MRCI) calculations. Comparing the resulting PESs with spin-orbit MRCI calculations, excellent agreement is found for the excited electronic states at all relevant geometries. The photodetachment spectrum of CH4 · F− is investigated via full-dimensional (12D) quantum dynamics calculations on the coupled PESs using the multi-layer multi-configurational time-dependent Hartree approach. Extending previous work [J. Palma and U. Manthe, J. Chem. Phys. 137, 044306 (2012)]10.1063/1.4737382, which was restricted to the dynamics on a single adiabatic PES, the contributions of the electronically excited states to the photodetachment spectrum are calculated and compared to experiment. Considering different experimental setups, good agreement between experiment and theory is found. Addressing questions raised in the previous work, the present dynamical calculations show that the main contribution to the second peak in the photodetachment spectrum results from electron detachment into the electronically excited states of the CH4F complex.
System to measure accurate temperature dependence of electric conductivity down to 20 K in ultrahigh vacuum
Authors: Sakai C. , Takeda S. N. , Daimon H.
Published: July 2013

We have developed the new in situ electrical-conductivity measurement system which can be operated in ultrahigh vacuum (UHV) with accurate temperature measurement down to 20 K. This system is mainly composed of a new sample-holder fixing mechanism, a new movable conductivity-measurement mechanism, a cryostat, and two receptors for sample- and four-probe holders. Sample-holder is pushed strongly against the receptor, which is connected to a cryostat, by using this new sample-holder fixing mechanism to obtain high thermal conductivity. Test pieces on the sample-holders have been cooled down to about 20 K using this fixing mechanism, although they were cooled down to only about 60 K without this mechanism. Four probes are able to be touched to a sample surface using this new movable conductivity-measurement mechanism for measuring electrical conductivity after making film on substrates or obtaining clean surfaces by cleavage, flashing, and so on. Accurate temperature measurement is possible since the sample can be transferred with a thermocouple and/or diode being attached directly to the sample. A single crystal of Bi-based copper oxide high-Tc superconductor (HTSC) was cleaved in UHV to obtain clean surface, and its superconducting critical temperature has been successfully measured in situ. The importance of in situ measurement of resistance in UHV was demonstrated for this HTSC before and after cesium (Cs) adsorption on its surface. The Tc onset increase and the Tc offset decrease by Cs adsorption were observed.
Tight-binding approach to strain-dependent DNA electronics
Authors: Malakooti Sadeq , Hedin Eric , Joe Yong
Published: July 2013

Small mechanical strain perturbations are considered in calculations of the poly(G)-poly(C) DNA molecular electronic structure, using a tight-binding framework in conjunction with the theories of Slater-Koster and linear elasticity. Results reveal a strain-induced band gap for DNA which is linearly dependent on the induced strain. Local density of states calculations expose that the contribution of the guanine-cytosine base pairs in the charge transport mechanism is significantly enhanced relative to the backbones when DNA is compressed. Transport investigations also disclose a strain-induced metal-semiconductor transition for the DNA molecule, which suggests possible potential uses for sensing applications.
Finite dimensional indecomposable modules for Schrödinger algebra
Authors: Wu Yuezhu
Published: July 2013

In this paper, we give a classification of finite dimensional indecomposable modules of the Schrödinger algebra.
Stacking fault expansion from basal plane dislocations converted into threading edge dislocations in 4H-SiC epilayers under high current stress
Authors: Konishi Kazuya , Yamamoto Shigehisa , Nakata Shuhei , Nakamura Yu , Nakanishi Yosuke , Tanaka Takanori , Mitani Yoichiro , Tomita Nobuyuki , Toyoda Yoshihiko , Yamakawa Satoshi
Published: July 2013

We evaluate the stacking faults (SFs) expansion from basal plane dislocations (BPDs) converted into threading edge dislocations (TEDs) under the current stress to the pn devices and analyzed the nucleation site of the SF by combined polishing, chemical etching in molten KOH, photoluminescence imaging, Focus ion beam, transmission electron microscopy, and Time-of-Flight secondary ion mass spectrometer techniques. It was found that the formation of SFs occurs upon the current stress levels of 400 A/cm2 where the diode area is not including BPDs in the drift layer after the high current stress, and the high current stress increases the SFs expansion density. It was also found the dependence of the junction temperature. The estimated activation energy for the expansion of SFs is Ea = 0.46 eV. The SF extends from the conversion point of the BPD into the TED within buffer layer. Even though BPDs converted into TEDs within the high doped buffer layer, SFs expand under high current stress.
Stationary self-focusing of Gaussian laser beam in relativistic thermal quantum plasma
Authors: Patil S. D. , Takale M. V.
Published: July 2013

In the present paper, we have employed the quantum dielectric response in thermal quantum plasma to model relativistic self-focusing of Gaussian laser beam in a plasma. We have presented an extensive parametric investigation of the dependence of beam-width parameter on distance of propagation in relativistic thermal quantum plasma. We have studied the role of Fermi temperature in the phenomenon of self-focusing. It is found that the quantum effects cause much higher oscillations of beam-width parameter and better relativistic focusing of laser beam in thermal quantum plasma in comparison with that in the relativistic cold quantum plasma and classical relativistic plasma. Our computations show more reliable results in comparison to the previous works.
A transient natural convection heat transfer model for geothermal borehole heat exchangers
Authors: Ghoreishi-Madiseh S. A. , Hassani F. P. , Mohammadian A. , Radziszewski P. H.
Published: July 2013

The effect of buoyancy-driven natural convection on the performance of ground-coupled heat exchangers of closed loop geothermal systems is investigated. The governing equations of continuity, momentum, and energy balance are derived, taking into account a porous ground medium fully saturated with liquid water. Boussinesq approximation is used to model the effect of buoyancy forces in water. A three-dimensional finite-volume discretization method over a structured mesh is used to solve the governing equations numerically. The performance of the ground-coupled heat exchanger system is assessed based on the rate of energy extraction and the outlet fluid temperature. The effects of hydraulic conductivity of the heat exchange medium and seasonal variations of heat load on the heat transfer phenomenon are studied. The results are evaluated by comparing them against the results of existing conduction-based heat transfer models. The influence of natural convection on the sustainable rate of heat extraction from a geothermal resource is underlined and interpreted.
Thermal modeling, energy and exergy analysis of animal feed solar cooker
Authors: Panwar N. L.
Published: July 2013

This study deals with thermal modeling and experimental validation of animal feed solar cooker. The experiment was conducted for 9 months and found that a theoretical temperature is 2 to 3 °C higher than experimentally recorded. The value of correlation (r) coefficient for all months was 0.999, indicating that the developed model is capable of predicting the water temperature close to experimental values. Energy and exergy assessment of the cooker was also carried out. The experimental energy and exergy efficiency varied in the range of 23.19% to 28.25% and 1. 79% to 2.47%, respectively. The corresponding theoretical efficiency varies in the range of 24.22% to 28.33% and 1.97% to 2.88%, respectively.
Collisional particle-in-cell modeling for energy transport accompanied by atomic processes in dense plasmas
Authors: Mishra R. , Leblanc P. , Sentoku Y. , Wei M. S. , Beg F. N.
Published: July 2013

Fully relativistic collisional Particle-in-Cell (PIC) code, PICLS, has been developed to study extreme energy density conditions produced in intense laser-solid interaction. Recent extensions to PICLS, such as the implementation of dynamic ionization, binary collisions in a partially ionized plasma, and radiative losses, enhance the efficacy of simulating intense laser plasma interaction and subsequent energy transport in resistive media. Different ionization models are introduced and benchmarked against each other to check the suitability of the model. The atomic physics models are critical to determine the energy deposition and transport in dense plasmas, especially when they consist of high Z (atomic number) materials. Finally we demonstrate the electron transport simulations to show the importance of target material on fast electron dynamics.
Hydrogen storage with titanium-functionalized graphene
Authors: Mashoff Torge , Takamura Makoto , Tanabe Shinichi , Hibino Hiroki , Beltram Fabio , Heun Stefan
Published: July 2013

We report on hydrogen adsorption and desorption on titanium-covered graphene in order to test theoretical proposals to use of graphene functionalized with metal atoms for hydrogen storage. At room temperature, titanium islands grow on graphene with an average diameter of about 10 nm. Samples were then loaded with hydrogen, and its desorption kinetics was studied by thermal desorption spectroscopy. We observe the desorption of hydrogen in the temperature range between 400 K and 700 K. Our results demonstrate the stability of hydrogen binding at room temperature and show that hydrogen desorbs at moderate temperatures in line with what is required for practical hydrogen-storage applications.
Electronic structure and magnetic properties of sub-3 nm diameter Mn-doped SnO2 nanocrystals and nanowires
Authors: Sabergharesou Tahereh , Wang Ting , Ju Ling , Radovanovic Pavle V.
Published: July 2013

Manganese-doped SnO2 nanocrystals and nanowires with diameters below SnO2 Bohr radius were synthesized by solution methods. X-ray absorption studies reveal that dopant ions are substitutionally incorporated as Mn2+ and Mn3+. Mn2+ is the dominant species at low doping levels, but the fraction of Mn3+ increases with doping concentration. Room-temperature ferromagnetism with the saturation moment of 0.27 μB/Mn is observed for nanocrystalline films containing high fraction of Mn2+ dopant, which is associated with hybridization of Mn2+ d-levels with a donor-impurity band. These results imply the possibility of manipulating magnetic interactions via dopant electronic structure and quantum confinement of the host lattice.
Direct deposition of aluminum oxide gate dielectric on graphene channel using nitrogen plasma treatment
Authors: Lim Taekyung , Kim Dongchool , Ju Sanghyun
Published: July 2013

Deposition of high-quality dielectric on a graphene channel is an essential technology to overcome structural constraints for the development of nano-electronic devices. In this study, we investigated a method for directly depositing aluminum oxide (Al2O3) on a graphene channel through nitrogen plasma treatment. The deposited Al2O3 thin film on graphene demonstrated excellent dielectric properties with negligible charge trapping and de-trapping in the gate insulator. A top-gate-structural graphene transistor was fabricated using Al2O3 as the gate dielectric with nitrogen plasma treatment on graphene channel region, and exhibited p-type transistor characteristics.
All-fiber ultrafast thulium-doped fiber ring laser with dissipative soliton and noise-like output in normal dispersion by single-wall carbon nanotubes
Authors: Wang QingQing , Chen Tong , Li Mingshan , Zhang Botao , Lu Yongfeng , Chen Kevin P.
Published: July 2013

An ultrafast thulium-doped fiber laser with large net normal dispersion has been developed to produce dissipative soliton and noise-like outputs at 1.9 μm. The mode-locked operation was enabled by using single-wall carbon nanotubes as saturable absorber for all-fiber configuration. Dissipative soliton in normal dispersion produced by the fiber laser oscillator was centered at 1947 nm with 4.1-nm FWHM bandwidth and 0.45 nJ/pulse. The output dissipative soliton pulses were compressed to 2.3 ps outside the laser cavity.
Selective oxidization cavity confinement for low threshold vertical cavity transistor laser
Authors: Wu M. K. , Liu M. , Tan F. , Feng M. , Holonyak N.
Published: July 2013

Data are presented for a low threshold n-p-n vertical cavity transistor laser (VCTL) with improved cavity confinement by trench opening and selective oxidation. The oxide-confined VCTL with a 6.5 × 7.5 μm2 oxide aperture demonstrates a threshold base current of 1.6 mA and an optical power of 150 μW at IB = 3 mA operating at −80 °C due to the mismatch between the quantum well emission peak and the resonant cavity optical mode. The VCTL operation switching from spontaneous to coherent stimulated emission is clearly observed in optical output power L-VCE characteristics. The collector output IC–VCE characteristics demonstrate the VCTL can lase in transistor's forward-active mode with a collector current gain β = 0.48.
Gd(III) doping effect on magnetization and water proton relaxivities in ultra small iron oxide nanoparticles
Authors: Choi Eun Sook , Xu Wenlong , Baek Myung Ju , Park Ja Young , Kim Joo Hyun , Chang Yongmin , Kim Tae Jeong , Lee Gang Ho
Published: July 2013

Two samples of ultra small Gd(III) doped iron oxide nanoparticles were prepared to investigate Gd(III) doping effect on longitudinal (r1) and transverse (r2) water proton relaxivities. Gd(III) doping mole percents were 0.2 and 0.4 for samples 1 and 2, respectively. Average particle diameters were 2.5 to 2.1 nm for samples 1 and 2, respectively. Reduced r1 and r2 values were observed in both samples. We attributed this to reduced magnetizations arising from opposing effect of Gd(III) to net magnetizations of Fe(III)/Fe(II) in oxide nanoparticles.
Characterization and comparison of human nuclear and cytosolic editomes
Authors: Chen Liang
Published: July 2013

Significance

RNA editing can alter the information content of genome sequences and increase transcriptome diversity. Global analyses of RNA editing remain challenging, largely due to the analytical barriers to separating editing events from errors in sequencing and alignment. Our computational statistical framework addresses these challenges and will also benefit other single-nucleotide level analyses of RNA-Seq data. Our results provide guidance for detecting nucleotide variants in RNA-Seq. We characterized human nuclear and cytosolic editomes and revealed relationships between editing and nucleocytoplasmic compartmentalization, microRNA regulation, and coding capacity. We also discovered that A-to-G editing mediates RNA memory of ancestral DNA alleles.
Rotavirus mRNAS are released by transcript-specific channels in the double-layered viral capsid
Authors: Periz Javier , Celma Cristina , Jing Bo , Pinkney Justin N. M. , Roy Polly , Kapanidis Achillefs N.
Published: July 2013

Rotaviruses are the single most common cause of fatal and severe childhood diarrheal illness worldwide (>125 million cases annually). Rotavirus shares structural and functional features with many viruses, such as the presence of segmented double-stranded RNA genomes selectively and tightly packed with a conserved number of transcription complexes in icosahedral capsids. Nascent transcripts exit the capsid through 12 channels, but it is unknown whether these channels specialize in specific transcripts or simply act as general exit conduits; a detailed description of this process is needed for understanding viral replication and genomic organization. To this end, we developed a single molecule assay for capturing and identifying transcripts extruded from transcriptionally active viral particles. Our findings support a model in which each channel specializes in extruding transcripts of a specific segment that in turn is linked to a single transcription complex. Our approach can be extended to study other viruses and transcription systems.