Indirect determination of the ratio R=σL/σT at small x from HERA data

The value of the deep inelastic scattering cross-section ratio R=σ _L /σ _T is found in the range 10⁻⁴⩽x⩽10⁻² from F ₂ and dF ₂/d ln Q ² HERA data using very simple relations based on perturbative QCD. Zh. éksp. Teor. Fiz. 112, 32–36 (July 1997) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

A QCD analysis of HERA and fixed target structure function data

The parton momentum density distributions of the proton are determined from a next-to-leading order QCD analysis of structure functions measured at HERA and by fixed target experiments. Also included are data on the difference of the up and down anti-quark distributions. The uncertainties in the parton densities, structure functions and related cross sections are estimated from the experimental errors and those on the input parameters of the fit. Several QCD predictions based on the parton densities obtained from this analysis are calculated and compared to data. Received: 21 December 1999 / Published online: 6 April 2000     

Beamforming using spatial matched filtering with annular arrays (L)

A linear array beamforming method for ultrasonic B-mode imaging using spatial matched filtering (SMF) and a rectangular aperture geometry was recently proposed Kim et al., [J. Acoust. Soc. Am. 120, 852-861 (2006)]. This letter extends those results to include circularly symmetric apertures. SMF applied to annular arrays can improve the lateral resolution and echo signal-to-noise ratio as compared with conventional dynamic-receive delay-sum beamforming. At high frequencies, where delay and sum beamforming is problematic, SMF showed greatly improved target contrast over an extended field of view.     

Efficient and accurate determination of the overall rotational diffusion tensor of a molecule from (15)N relaxation data using computer program ROTDIF

We present a computer program ROTDIF for efficient determination of a complete rotational diffusion tensor of a molecule from NMR relaxation data. The derivation of the rotational diffusion tensor in the case of a fully anisotropic model is based on a six-dimensional search, which could be very time consuming, particularly if a grid search in the Euler angle space is involved. Here, we use an efficient Levenberg-Marquardt algorithm combined with Monte Carlo generation of initial guesses. The result is a dramatic, up to 50-fold improvement in the computational efficiency over the previous approaches. This method is demonstrated on a computer-generated and real protein systems. We also address the issue of sensitivity of the diffusion tensor determination from (15)N relaxation measurements to experimental errors in the relaxation rates and discuss possible artifacts from applying higher-symmetry tensor model and how to recognize them.     

Precise determination of the f0(600) and f0(980) pole parameters from a dispersive data analysis

We use our latest dispersive analysis of ππ scattering data and the very recent K(?4) experimental results to obtain the mass, width, and couplings of the two lightest scalar-isoscalar resonances. These parameters are defined from their associated poles in the complex plane. The analytic continuation to the complex plane is made in a model-independent way by means of once- and twice-subtracted dispersion relations for the partial waves, without any other theoretical assumption. We find the f(0)(600) pole at (457(-13))+14))-i(279(-7)(+11)) MeV and that of the f(0)(980) at (996 ± 7)-i(25(-6)(+10)) MeV, whereas their respective couplings to two pions are 3.59(-0.13)(+0.11) and 2.3 ± 0.2 GeV.     

A scheme for data encryption and transmission using temporal correlation-based spectral switches

We present a method for data encoding in terms of spectral shifts in the source spectra. The spectral switching of polychromatic light due to temporal correlation, around the intensity minima in a Michelson Interferometer (MI) has been utilized for this purpose. The potential application of the encoding method for free space communication is described in detail. The advantages of this method are compared with the proposed schemes of data communication using spectral switches. The experimental constraints of this method are also discussed.     

A scheme for the interpretation of data from instrumented offshore platforms

A procedure is presented for estimating the key parameters associated with the dynamic behaviour of deepwater gravity platforms. Efficient modelling of the coupled soil/structure/fluid system is achieved by the method of component modes. This permits accurate analysis of the dynamic behaviour of the platform with an idealization having only a few co-ordinates. Full-scale measurements (in the form of direct and cross spectral densities of water surface elevation, overturning moment, deck displacement, etc.) may then be used to obtain “best fit” estimates of the unknown stiffness and damping parameters. Computed results demonstrating the technique are presented, in which simulated data from a platform are used to back-figure the stiffness and damping associated with structure and foundation.     

On the possibility of measuringF L (x,Q 2) at HERA using radiative events

It is shown that a significant measurement of the longitudinal structure functionF _L (x, Q ²) can be performed at HERA, forQ ²=2 GeV² andQ ²=5 GeV² and forx around 10^?4, using radiative events with hard photon emission collinear to the incident lepton beam, under the present running conditions and with an integrated luminosity of 10 pb^?1. The influence of experimental conditions is discussed.     

Simple and accurate determination of global tau(R) in proteins using (13)C or (15)N relaxation data

In the study of protein dynamics by (13)C or (15)N relaxation measurements different models from the Lipari-Szabo formalism are used in order to determine the motion parameters. The global rotational correlation time tau(R) of the molecule must be estimated prior to the analysis. In this Communication, the authors propose a new approach in determining an accurate value for tau(R) in order to realize the best fit of R(2) for the whole sequence of the protein, regardless of the different type of motions atoms may experience. The method first determines the highly structured regions of the sequence. For each corresponding site, the Lipari-Szabo parameters are calculated for R(1) and NOE, using an arbitrary value for tau(R). The chi(2) for R(2), summed over the selected sites, shows a clear minimum, as a function of tau(R). This minimum is used to better estimate a proper value for tau(R).     

A novel data hiding and reversible scheme using SMN blocks in VQ-compressed images

Data hiding is a technique for embedding secret data into cover media. It is important to multimedia security and has been widely studied. Reversible data hiding methods are becoming prevalent in the area because they can reconstruct the original cover image while extracting the embedded data. In this paper, we propose a new reversible method for vector quantization (VQ) compressed images. Our method takes advantages of the relationship among the side match neighbouring (SMN) blocks to achieve reversibility. The experimental results show that the proposed method has higher compression rate and larger capacity than other existing reversible methods.     

A high-order accurate hybrid scheme using a central flux scheme and a WENO scheme for compressible flowfield analysis

A high-order accurate hybrid central-WENO scheme is proposed. The fifth order WENO scheme [G.S. Jiang, C.W. Shu, Efficient implementation of weighted ENO schemes, J. Comput. Phys. 126 (1996) 202–228] is divided into two parts, a central flux part and a numerical dissipation part, and is coupled with a central flux scheme. Two sub-schemes, the WENO scheme and the central flux scheme, are hybridized by means of a weighting function that indicates the local smoothness of the flowfields. The derived hybrid central-WENO scheme is written as a combination of the central flux scheme and the numerical dissipation of the fifth order WENO scheme, which is controlled adaptively by a weighting function. The structure of the proposed hybrid central-WENO scheme is similar to that of the YSD-type filter scheme [H.C. Yee, N.D. Sandham, M.J. Djomehri, Low-dissipative high-order shock-capturing methods using characteristic-based filters, J. Comput. Phys. 150 (1999) 199–238]. Therefore, the proposed hybrid scheme has also certain merits that the YSD-type filter scheme has. The accuracy and efficiency of the developed hybrid central-WENO scheme are investigated through numerical experiments on inviscid and viscous problems. Numerical results show that the proposed hybrid central-WENO scheme can resolve flow features extremely well.     

Numerical (error) issues on compressible multicomponent flows using a high-order differencing scheme: Weighted compact nonlinear scheme

A weighted compact nonlinear scheme (WCNS) is applied to numerical simulations of compressible multicomponent flows, and four different implementations (fully or quasi-conservative forms and conservative or primitive variables interpolations) are examined in order to investigate numerical oscillation generated in each implementation. The results show that the different types of numerical oscillation in pressure field are generated when fully conservative form or interpolation of conservative variables is selected, while quasi-conservative form generally has poor mass conservation property. The WCNS implementation with quasi-conservative form and interpolation of primitive variables can suppress these oscillations similar to previous finite volume WENO scheme, despite the present scheme is finite difference formulation and computationally cheaper for multi-dimensional problems. Series of analysis conducted in this study show that the numerical oscillation due to fully conservative form is generated only in initial flow fields, while the numerical oscillation due to interpolation of conservative variables exists during the computations, which leads to significant spurious numerical oscillations near interfaces of different component of fluids. The error due to fully conservative form can be greatly reduced by smoothing interface, while the numerical oscillation due to interpolation of conservative variables cannot be significantly reduced. The primitive variable interpolation is, therefore, considered to be better choice for compressible multicomponent flows in the framework of WCNS. Meanwhile better choice of fully or quasi-conservative form depends on a situation because the error due to fully conservative form can be suppressed by smoothed interface and because quasi-conservative form eliminates all the numerical oscillation but has poor mass conservation.     

Precise orbit determination of a maneuvered GEO satellite using CAPS ranging data

Wheel-off-loadings and orbital maneuvers of the GEO satellite result in additional accelerations to the satellite itself. Complex and difficult to model, these time varying accelerations are an important error source of precise orbit determination (POD). In most POD practices, only non-maneuver orbital arcs are treated. However, for some applications such as satellite navigation RDSS services, uninterrupted orbital ephemeris is demanded, requiring the development of POD strategies to be processed both during and after an orbital maneuver. We in this paper study the POD for a maneuvered GEO satellite, using high precision and high sampling rate ranging data obtained with Chinese Area Positioning System (CAPS). The strategy of long arc POD including maneuver arcs is studied by using telemetry data to model the maneuver thrust process. Combining the thrust and other orbital perturbations, a long arc of 6 days’ CAPS ranging data is analyzed. If the telemetry data are not available or contain significant errors, attempts are made to estimate thrusting parameters using CAPS ranging data in the POD as an alternative to properly account for the maneuver. Two strategies achieve reasonably good data fitting level in the tested arc with the maximal position difference being about 20 m. Supported by the National Natural Science Foundation of China (Grant No. 10703011) and the Science & Technology Commission of Shanghai Municipality of China (Grant No. 06DZ22101)     

Measurement of the proton structure functionF2 from the 1993 HERA data

The ZEUS detector has been used to measure the proton structure functionF ₂. During 1993 HERA collided 26.7 GeV electrons on 820 GeV protons. The data sample corresponds to an integrated luminosity of 0.54 pb^–1, representing a twenty fold increase in statistics compared to that of 1992. Results are presented for 7Q ²<>⁴ GeV² andx values as low as 3×10^–4. The rapid rise inF ₂ asx decreases observed previously is now studied in greater detail and persists forQ ² values up to 500 GeV².supported by Worldlab, Lausanne, Switzerland     

Ultrasensitive and selective spectrofluorimetric determination of Hg(II) using a dimercaptothiadiazole fluorophore

The present work describes the ultrasensitive and selective spectrofluorimetric determination of Hg(II) using 2,5-dimercaptothiadiazole (DMT) as a fluorophore. DMT shows an emission maximum at 435 nm while exciting at 330 nm. The colorless solution of DMT changes into a highly emittive yellow color immediately after the addition of 0.5 μM Hg(II) and nearly 245-fold increase in emission intensity at 435 nm was observed. These changes were ascribed to the complex formation between Hg(II) and DMT. Based on the fluorescence enhancement, the concentration of Hg(II) was determined. The binding constant value (K_A=1.8620×10⁴ mol⁻¹ L) suggests that there is a strong binding force between Hg(II) and DMT. The fluorescence quantum yield of DMT-Hg(II) complex was found to be 4-fold higher than that of DMT, indicating that the DMT-Hg(II) complex was highly emittive than the DMT. Interestingly, the emission intensity was increased even in the presence of 0.1 pM Hg(II). The fluorophore showed an extreme selectivity towards 100 nM Hg(II) in the presence of 50,000-fold higher concentrations of Na⁺, K⁺, Ca²⁺, Mg²⁺, Fe²⁺, Fe³⁺, Cd²⁺, Cr³⁺, Mn²⁺, Zn²⁺, Co²⁺, Ni²⁺, Cl⁻, SO₄²⁻, NO₃⁻ ions and 1000-, 500- and 200-fold higher concentrations of Cu²⁺, Pb²⁺ and Ag⁺ ions, respectively, as interferences. The lowest detection of 18 pg L⁻¹ Hg(II) (LOD=3S/m) was achieved for the first time using DMT by fluorimetry. The proposed method was successfully utilized for the determination of Hg(II) in tap water, river water and industrial waste water samples.     

MiniBooNE and LSND data: non-standard neutrino interactions in a (3+1) scheme versus (3+2) oscillations

Journal of High Energy Physics - We consider the cosmology of a model in which the dark matter is part of a nonminimal hidden sector which is not in thermal equilibrium with the standard model...