Smooth Evolution Research Articles

High-precision measurements of seawater Pb isotope compositions by double spike thermal ionization mass spectrometry

A new method for the determination of seawater Pb isotope compositions and concentrations was developed, which combines and optimizes previously published protocols for the separation and isotopic analysis of this element. For isotopic analysis, the procedure involves initial separation of Pb from 1 to 2L of seawater by co-precipitation with Mg hydroxide and further purification by a two stage anion exchange procedure. The Pb isotope measurements are subsequently carried out by thermal ionization mass spectrometry using a 207Pb–204Pb double spike for correction of instrumental mass fractionation. These methods are associated with a total procedural Pb blank of 28±21pg (1sd) and typical Pb recoveries of 40–60%. The Pb concentrations are determined by isotope dilution (ID) on 50mL of seawater, using a simplified version of above methods. Analyses of multiple aliquots of six seawater samples yield a reproducibility of about ±1 to ±10% (1sd) for Pb concentrations of between 7 and 50pmol/kg, where precision was primarily limited by the uncertainty of the blank correction (12±4pg; 1sd). For the Pb isotope analyses, typical reproducibilities (±2sd) of 700–1500ppm and 1000–2000ppm were achieved for 207Pb/206Pb, 208Pb/206Pb and 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb, respectively. These results are superior to literature data that were obtained using plasma source mass spectrometry and they are at least a factor of five more precise for ratios involving the minor 204Pb isotope. Both Pb concentration and isotope data, furthermore, show good agreement with published results for two seawater intercomparison samples of the GEOTRACES program. Finally, the new methods were applied to a seawater depth profile from the eastern South Atlantic. Both Pb contents and isotope compositions display a smooth evolution with depth, and no obvious outliers. Compared to previous Pb isotope data for seawater, the 206Pb/204Pb ratios are well correlated with 207Pb/206Pb, underlining the significant improvement achieved in the measurement of the minor 204Pb isotope.

A smooth evolution to next generation PON based on orthogonal modulation

A smooth evolution to next generation PON based orthogonal modulation is proposed. The newly added next generation PON reuses the existing infrastructure and coexists with the current PON. To eliminate any change requirement for the existing PON, orthogonal modulation is applied for new PON downstream. The crosstalk to the existing PON signal from coexisting is much reduced by orthogonal modulation of new PON. The experimental results show very little power penalty of coexisting. Error free operation is achieved for all signals.

Unsupervised joint decomposition of a spectroscopic signal sequence

This paper addresses the problem of decomposing a sequence of spectroscopic signals. Data are a series of signals modeled as a noisy sum of parametric peaks. We aim to estimate the peak parameters given that they change slowly between two contiguous signals. The key idea is to decompose the whole sequence rather than each signal independently. The problem is set within a Bayesian framework. The peaks with similar evolution are gathered into groups and a Markovian prior on the peak parameters of a same group is used to favor a smooth evolution of the peaks. In addition, the peak number and the group number are unknown and have to be estimated (the number of peaks in two contiguous signals change if peaks vanish). Therefore, the posterior distribution is sampled with a reversible jump Markov chain Monte Carlo algorithm. Simulations conducted on synthetic and real photoelectron data illustrate the performance of the method.

CCNxTomcat: An extended web server for Content-Centric Networking

TCP/IP networks are the backbone of the Internet today, and browser/server is the mainstream web architecture on it. Recently, Content-Centric Networking (CCN) has emerged as a clean-slate future network architecture, with totally different protocols than a host-based TCP/IP network. However, current web servers are mainly designed for HTTP over a TCP/IP network and can not directly support CCN-based web applications. Therefore, how to effectively support the dominant browser-based web applications is a key to the success of CCN. Instead of providing a transitional HTTP/CCN transforming gateway or proxy, we design and develop the first practical CCN-enabled web server (called CCNxTomcat) based on open source Apache Tomcat and the CCNx library to natively support CCN-based web applications. The CCN functions are integrated into the web server for content distribution by seamlessly coordinating with the underlying CCN network. To support legacy applications and a smooth evolution from an IP network to CCN, CCNxTomcat also supports the HTTP protocol besides the CCN. Experimental results show that CCNxTomcat outperforms the existing HTTP/CCN proxy implementations by 58% in a single request, and by a factor of three in 1000 concurrent requests, in terms of throughput. Furthermore, we design and implement a novel cache (called ccncache) for the Servlet response, performing name lookups for Content Packets with a high efficiency. The results indicate that ccncache is 2.5 times faster than the existing CCNx Content Store, with only 30% additional memory consumption. In addition, a real CCN-based web application is deployed on a CCN experimental network, which validates the applicability of CCNxTomcat.

RAPID DECLINE OF Lyα EMISSION TOWARD THE REIONIZATION ERA

The observed deficit of strongly Lyman-alpha emitting galaxies at z>6.5 is attributed to either increasing neutral hydrogen in the intergalactic medium (IGM) and/or to the evolving galaxy properties. To investigate this, we have performed very deep near-IR spectroscopy of z>7 galaxies using MOSFIRE on the Keck-I Telescope. We measure the Lyman-alpha fraction at z~8 (combined photometric redshift peak at z=7.7) using two methods. First, we derived NLy{\alpha}/Ntot directly using extensive simulations to correct for incompleteness. Second, we used a Bayesian formalism (introduced by Treu et al. 2012) that compares the z>7 galaxy spectra to models of the Lyman-alpha equivalent width (WLy{\alpha}) distribution at z~6. We explored two simple evolutionary scenarios: smooth evolution where Lyman-alpha is attenuated in all galaxies by a constant factor (perhaps owing to processes from galaxy evolution or a slowly increasing IGM opacity), and patchy evolution where Lyman-alpha is blocked in some fraction of galaxies (perhaps due to the IGM being opaque along only some fraction of sightlines). The Bayesian formalism places stronger constraints compared with the direct method. Combining our data with that in the literature we find that at z~8 the Lyman-alpha fraction has dropped by a factor >3(84% confidence interval) using both the smooth and patchy scenarios compared to the z~6 values. Furthermore, we find a tentative evidence that the data favor the patchy scenario over smooth (with "positive" Bayesian evidence), extending trends observed at z~7 to higher redshift. If this decrease is a result of reionization as predicted by theory, then our data imply the volume averaged neutral hydrogen fraction in the IGM to be >0.3 suggesting that the reionization of the universe is in progress at z~8.

Comparative study of the mechanical properties of nanostructured thin films on stretchable substrates

Comparative studies of the mechanical behavior between copper, tungsten, and W/Cu nanocomposite based on copper dispersoïd thin films were performed under in-situ controlled tensile equi-biaxial loadings using both synchrotron X-ray diffraction and digital image correlation techniques. The films first deform elastically with the lattice strain equal to the true strain given by digital image correlation measurements. The Cu single thin film intrinsic elastic limit of 0.27% is determined below the apparent elastic limit of W and W/Cu nanocomposite thin films, 0.30% and 0.49%, respectively. This difference is found to be driven by the existence of as-deposited residual stresses. Above the elastic limit on the lattice strain-true strain curves, we discriminate two different behaviors presumably footprints of plasticity and fracture. The Cu thin film shows a large transition domain (0.60% true strain range) to a plateau with a smooth evolution of the curve which is associated to peak broadening. In contrast, W and W/Cu nanocomposite thin films show a less smooth and reduced transition domain (0.30% true strain range) to a plateau with no peak broadening. These observations indicate that copper thin film shows some ductility while tungsten/copper nanocomposites thin films are brittle. Fracture resistance of W/Cu nanocomposite thin film is improved thanks to the high compressive residual stress and the elimination of the metastable β-W phase.

Key Role of End-Capping Groups in Optoelectronic Properties of Poly-p-phenylene Cation Radicals.

Poly-p-phenylenes (PPs) are prototype systems for understanding the charge transport in π-conjugated polymers. In a combined computational and experimental study, we demonstrate that the smooth evolution of redox and optoelectronic properties of PP cation radicals toward the polymeric limit can be significantly altered by electron-donating iso-alkyl and iso-alkoxy end-capping groups. A multiparabolic model (MPM) developed and validated here rationalizes this unexpected effect by interplay of the two modes of hole stabilization: due to the framework of equivalent p-phenylene units and due to the electron-donating end-capping groups. A symmetric, bell-shaped hole in unsubstituted PPs becomes either slightly skewed and shifted toward an end of the molecule in iso-alkyl-capped PPs or highly deformed and concentrated on a terminal unit in PPs with strongly electron-donating iso-alkoxy capping groups. The MPM shows that the observed linear 1/n evolution of the PP cation radical properties toward the polymer limit originates from the hole stabilization due to the growing chain of p-phenylene units, while shifting of the hole toward electron-donating end-capping groups leads to early breakdown of these 1/n dependencies. These insights, along with the readily applicable and flexible multistate parabolic model, can guide studies of complex donor–spacer–acceptor systems and doped molecular wires to aid the design of the next generation materials for long-range charge transport and photovoltaic applications.

A smooth evolution scheme to remodulated WDM‐PON based on POLSK/ASK orthogonal modulation

ABSTRACTA smooth evolution scheme from legacy time division multiplexing passive optical network to the next generation wavelength division multiplexing passive optical network using polarization shift keying/amplitude shift keying orthogonal modulation is proposed and experimentally demonstrated. Clear eye diagrams and bit‐error‐rate performance show crosstalk is small. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2598–2601, 2014

Conducting Surveys and Data Collection: From Traditional to Mobile and SMS-based Surveys

F resh, bias-free and valid data collected using different survey modes is considered an essential requirement for smooth functioning and evolution of an organization . Surveys play a major role in making in-time correct decisions and generating reports. The aim of this study is to compare and investigate state-of-the-art in different survey modes including print, email, online, mobile and SMS-based surveys. Results indicated that existing methods are neither complete nor sufficient to fulfil the overall requirements of an organization which primarily rely on surveys. Also, it shows that SMS is a dominant method for data collection due to its pervasiveness. However, existing SMS-based data collection has limitations like limited number of characters per SMS, single question per SMS and lake of multimedia support. Recent trends in data collection emphasis on data collection applications for smart phones. However, in developing countries low-end mobile devices are still extensively used which makes the data collection difficult from man in the street. The paper conclude that existing survey modes and methods should be improved to get maximum responses quickly in low cost manner. The study has contributed to the area of surveying and data collection by analysing different factors such as cost, time and response rate. The results of this study can help practitioners in creating a more successful surveying method for data collection that can be effectively used for low budget projects in developed as well as developing countries.

NDNBrowser: An extended web browser for named data networking

Web applications have become one of the fundamental Internet services. How to effectively support the popular browser-based web applications is a key to success for Named Data Networking (NDN). However, since NDN has a totally different running mechanism from the traditional IP network, the existing web browsers mainly designed for the HTTP protocol and the TCP/IP-based Internet rather than named data networking, cannot communicate with NDN routers directly and do not inherently support the NDN-based web applications. Instead of providing a browser add-on or HTTP–NDN proxy/gateway, we designed and developed a complete NDNBrowser based on open source WebKit to natively support NDN-based web applications in the web browser kernel. Some inherent NDN features are seamlessly integrated into the browser to support the direct interactions between web browser and NDN network. Considering backwards compatibility and smooth network evolution, the NDNBrowser enables content fetching and rendering by both ‘ccnx:/’ and ‘http:/’ schemes URI in HTML, CSS and JavaScript simultaneously. Experimental results show that the NDNBrowser outperforms existing NDN.JS and HTTP–NDN proxy/gateway implementations by 19× and 5× respectively in terms of throughput. Finally, a real NDN-based web application is deployed on a NDN experimental network in our campus environment for network innovations to verify the practicability of NDNBrowser.

Double field theory inspired cosmology

Double field theory proposes a generalized spacetime actionpossessing manifest T-duality on the level of component fields. Wecalculate the cosmological solutions of double field theory withvanishing Kalb-Ramond field. It turns out that double field theoryprovides a more consistent way to construct cosmological solutionsthan the standard string cosmology. We construct solutions for vanishing and non-vanishing symmetry preserving dilaton potentials. The solutions assemblethe pre- and post-big bang evolutions in one single line element.Our results show a smooth evolution from an anisotropic early stage to an isotropic phase without any special initial conditions in contrast to previous models. In addition, we demonstrate that the contraction of the dual space automatically leads to both an inflation phase and a decelerated expansion of the ordinary space during different evolution stages.

Constraints on the star-formation rate ofz~ 3 LBGs with measured metallicity in the CANDELS GOODS-South field

We analyse 14 LBGs at z~2.8-3.8 constituting the only sample where both a spectroscopic measurement of their metallicity and deep IR observations (CANDELS+HUGS survey) are available. Fixing the metallicity of population synthesis models to the observed values, we determine best-fit physical parameters under different assumptions about the star-formation history and also consider the effect of nebular emission. For comparison we determine the UV slope of the objects, and use it to estimate their SFR_UV99 by correcting the UV luminosity following Meurer et al. (1999). A comparison between SFR obtained through SED-fitting (SFR_fit) and the SFR_UV99 shows that the latter are underestimated by a factor 2-10, regardless of the assumed SFH. Other SFR indicators (radio, far-IR, X-ray, recombination lines) coherently indicate SFRs a factor of 2-4 larger than SFR_UV99 and in closer agreement with SFR_fit. This discrepancy is due to the solar metallicity implied by the usual beta-A1600 conversion factor. We propose a refined relation, appropriate for sub-solar metallicity LBGs: A1600 = 5.32+1.99beta. This relation reconciles the dust-corrected UV with the SED-fitting and the other SFR indicators. We show that the fact that z~3 galaxies have sub-solar metallicity implies an upward revision by a factor of ~1.5-2 of the global SFRD, depending on the assumptions about the age of the stellar populations. We find very young best-fit ages (10-500 Myrs) for all our objects. From a careful examination of the uncertainties in the fit and the amplitude of the Balmer break we conclude that there is little evidence of the presence of old stellar population in at least half of the LBGs in our sample, suggesting that these objects are probably caught during a huge star-formation burst, rather than being the result of a smooth evolution.

Mott-superfluid transition for spin-orbit-coupled bosons in one-dimensional optical lattices

We study the effects of spin-orbit coupling on the Mott-superfluid transition of bosons in a one-dimensional optical lattice. We determine the strong-coupling magnetic phase diagram by a combination of exact analytic and numerical means. Smooth evolution of the magnetic structure into the superfluid phases is investigated with the density matrix renormalization group technique. Other magnetic phases are seen and phase transitions between them within the superfluid regime are discussed. Possible experimental detection is discussed.

Variable-flip-angle single-slab 3D GRASE imaging with phase-independent image reconstruction

To develop a single-slab three-dimensional variable-flip-angle gradient- and spin-echo pulse sequence with phase-independent reconstruction that is highly energy- or encoding-efficient for high resolution isotropic imaging at high magnetic field. Amplitude modulation in the proposed pulse sequence was alleviated using a variable-flip-angle induced smooth signal evolution along the long echo train. To avoid phase modulation, instead of directly interleaving phase encoding signals with different off-resonance induced phase accumulation over multiple echoes, phase-independent image reconstruction was performed, wherein each echo image was separately reconstructed using convolution-interpolation with echo-interleaving self-calibration and then combined. Numerical and experimental studies were performed at 3.0 T for generation of clinical T2 -weighted contrast to investigate the effectiveness of the proposed method over existing methods. Compared with conventional techniques, the proposed method produces smooth amplitude variation, no ghosting artifacts (no phase modulation), and competitive signal-to-noise ratio. An energy-efficient variable-flip-angle gradient- and spin-echo reduces specific absorption rate by 71% without significant loss of signal-to-noise ratio, while an encoding-efficient one decreases imaging time by 54% with a slight loss of signal-to-noise ratio. We successfully demonstrated that the proposed variable-flip-angle gradient- and spin-echo can be a highly promising energy- or encoding-efficient alternative for high resolution isotropic imaging.

Structural Characterization of a Composition Tolerant Bulk Heterojunction Blend

The ratio of the donor and acceptor components in bulk heterojunction (BHJ) organic solar cells is a key parameter for achieving optimal power conversion efficiency (PCE). However, it has been recently found that a few BHJ blends have compositional tolerance and achieve high performance in a wide range of donor to acceptor ratios. For instance, the X2:PC61BM system, where X2 is a molecular donor of intermediate dimensions, exhibits a PCE of 6.6%. Its PCE is relatively insensitive to the blend ratio over the range from 7:3 to 4:6. The effect of blend ratio of X2/PC61BM on morphology and device performance is therefore systematically investigated by using the structural characterization techniques of energy‐filtered transmission energy microscopy (EF‐TEM), resonant soft X‐ray scattering (R‐SoXS) and grazing incidence wide angle X‐ray scattering (GIWAXS). Changes in blend ratio do not lead to obvious differences in morphology, as revealed by R‐SoXS and EF‐TEM. Rather, there is a smooth evolution of a connected structure with decreasing domain spacing from 8:2 to 6:4 blend ratios. Domain spacing remains constant from 6:4 to 4:6 blend ratios, which suggests the presence of continuous phases with proper domain size that may provide access for charge carriers to reach their corresponding electrodes.

A Smooth and Gradual Evolution to Next Generation PON Based on Simple Line-Coding

We propose a smooth and gradual evolution method to next generation passive optical network (PON) based on simple line-coding. At the beginning, a new OLT and some new ONUs are added into the existing PON without changing the existing ONUs. The evolution is gradual. The existing ONUs can be upgraded with demand. The coding is operated by software and requires no extra equipment. During different evolution stages, different line-codes are applied to reduce the crosstalk induced by the upgrade service to the existing service. The crosstalk is tested and shown not serious in the experiment.

X-ray photoemission, calorimetric, and electrical transport properties of CeCu4MnyAl1−y

We report the X-ray photoemission spectra (XPS) and the electrical resistivity measurements for the transition Kondo lattice – spin-glass (SG) in the series CeCu4MnyAl1−y. The study includes additionally the low temperature (down to T=400mK) heat capacity results. The XPS measurements revealed that the Ce 4f states are well localized. Electrical resistivity studies illustrate a smooth evolution from the ∼ −lnT relation to the metallic behaviour with the increase of the Mn content. Moreover, the specific heat has been analysed considering the electronic, phonon, Schottky (Crystal Electric Field – CEF), Kondo, and SG contributions. The assumption that the CEF splitting of the energy levels is similar for all the compositions allowed us to estimate the SG and Kondo contribution to the heat capacity. Additionally, the neutron diffraction experiment on the parent CeCu4Mn compound has confirmed that it does not show a long-range magnetic order.

The Model Reference Adaptive Control of the DC Electric Drive System

Due to the parametric and structural uncertainty of the DC drive system, an adaptive control method is necessary. Therefore, an original model reference adaptive control (MRAC) for DC drives is proposed in this paper. MRAC ensures on-line adjustment of the control parameters with DC machine parameter variation. The proposed adaptive control structure provides regulating advantages: asymptotic cancellation of the tracking error, fast and smooth evolution towards the origin of the phase plan due to a sliding mode switching k-sigmoid function. The reference model can be a real strictly positive function (the tracking error is also the identification error) as its order is relatively higher than one degree. For this reason, the synthesis of the adaptive control will use a different type of error called augmented or enhanced error. The DC machine with separate excitation is fed at a constant flux. This adaptive control law assures robustness to external perturbations and to unmodelled dynamics.

Scalar hyperbolic PDE simulations and coupling strategies

We report on grid-adaptive, multi-dimensional simulations for hyperbolic PDEs, with a deliberate focus on the analytically tractable scalar case. Motivated by recent efforts towards multi-physics simulation strategies, we investigate a variety of coupling strategies for numerically solving hyperbolic partial differential equations (PDEs). We use adaptive mesh refinement in combination with shock-capturing spatio-temporal discretizations, and first present accuracy and validation tests on both smooth and shock-dominated evolutions. To investigate the feasibility of coupling means for multi-physics simulations, we then introduce new reference tests where spatially different flux prescriptions require coupling strategies across the domains where local advection, Burgers or nonconvex behavior is imposed. For these nonlinear single scalar equations, we can illustrate and analytically explain the evolutions obtained when handling cases where fluxes differ in spatially non-overlapping regions. We discuss both conservative and non-conservative ways of coupling across the region boundaries. When coupling scalar conservation laws where the characteristic speeds change discontinuously across the regional boundaries, these two strategies yield differing, but mathematically sound, solution behaviors. Their relevance for multi-physics simulations where one couples systems of (hyperbolic) PDEs is discussed.

THE AFTERGLOW OF GRB 130427A FROM 1 TO 1016GHz

We present multiwavelength observations of the afterglow of GRB 130427A, the brightest (in total fluence) gamma-ray burst of the past 29 years. Optical spectroscopy from Gemini-North reveals the redshift of the GRB to be z=0.340, indicating that its unprecedented brightness is primarily the result of its relatively close proximity to Earth; the intrinsic luminosities of both the GRB and its afterglow are not extreme in comparison to other bright GRBs. We present a large suite of multiwavelength observations spanning from 300 s to 130 d after the burst and demonstrate that the afterglow shows relatively simple, smooth evolution at all frequencies with no significant late-time flaring or rebrightening activity. The entire dataset from 1 GHz to 10 GeV can be modeled as synchrotron emission from a combination of reverse and forward shocks in good agreement with the standard afterglow model, providing strong support to the applicability of the underlying theory and clarifying the nature of the GeV emission observed to last for minutes to hours following other very bright GRBs. A tenuous, wind-stratified circumburst density profile is required by the observations, suggesting a massive-star progenitor with a low mass-loss rate, perhaps due to low metallicity. GRBs similar in nature to GRB 130427A, inhabiting low-density media and exhibiting strong reverse shocks, are probably not uncommon but may have been difficult to recognize in the past due to their relatively faint late-time radio emission; more such events should be found in abundance by the new generation of sensitive radio and millimeter instruments.