bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of13C/12C ratios of endogenous urinary 5‐amino‐imidazole‐4‐carboxamide 1β‐D‐ribofuranoside (AICAR)
Authors: Piper Thomas , Thomas Andreas , Baume Norbert , Sobolevsky Timothy , Saugy Martial , Rodchenkov Grigory , Schänzer Wilhelm , Thevis Mario 
Published: April 2014

RATIONALEAICAR (5‐aminoimidazole‐4‐carboxamide 1β‐D‐ribofuranoside) is prohibited in sport according to rules established by the World Anti‐Doping Agency. Doping control laboratories identify samples where AICAR abuse is suspected by measuring its urinary concentration and comparing the observed level with naturally occurring concentrations. As the inter‐individual variance of urinary AICAR concentrations is large, this approach requires a complementary method to unambiguously prove the exogenous origin of AICAR. Therefore, a method for the determination of carbon isotope ratios (CIRs) of urinary AICAR has been developed and validated.METHODSConcentrated urine samples were fractionated by means of liquid chromatography for analyte cleanup. Derivatization of AICAR yielding the trimethylsilylated analog was necessary to enable CIR determinations by gas chromatography/combustion/isotope ratio mass spectrometry. The method was tested for its repeatability and stability over time and a linear mixing model was applied to test for possible isotopic discrimination. A reference population of n = 63 males and females was investigated to calculate appropriate reference limits to differentiate endogenous from exogenous urinary AICAR. These limits were tested by an AICAR elimination study.RESULTSThe developed method fulfills all the requirements for adequate sports drug testing and was found to be fit for purpose. The investigated reference population showed a larger variability in the CIR of AICAR than of the endogenous steroids. Nevertheless, the calculated thresholds for differences between AICAR and endogenous steroids can be applied straightforwardly to evaluate suspicious doping control samples with the same statistical confidence as established e.g. for testosterone misuse. These thresholds enabled the detection of a single oral AICAR administration for more than 40 h.CONCLUSIONSDetermination of thee CIRs is the method of choice to distinguish between an endogenous and an exogenous source of urinary AICAR. The developed method will enable investigations into doping control samples with elevated urinary concentrations of AICAR and clearly differentiate between naturally produced/elevated and illicitly administered AICAR. Copyright © 2014 John Wiley & Sons, Ltd.
Electrospray ionization tandem mass spectrometry study of six isomeric cationic amphiphiles with ester/amide linker
Authors: Vijay Darshan D. , Chandar B. G. N. , Srujan M. , Chaudhuri A. , Prabhakar S. 
Published: April 2014

RATIONALEIsomeric cationic amphiphiles differing only in the orientation of the linker group have been demonstrated to possess dramatically changed gene transfer efficacies. Studies aimed at understanding structure‐stability correlations of such isomeric cationic amphiphiles at the molecular level are yet to be undertaken. Such studies may throw significant new insights into the mechanistic origin on their contrasting bioactivities.METHODSElectrospray ionization mass spectrometry (ESI‐MS) and multi‐stage tandem mass spectrometric (MSn) experiments were performed on a LCQ ion trap mass spectrometer. The decomposition pathway was confirmed by high‐resolution mass spectrometry data from a quadrupole time‐of‐flight (Q‐TOF) mass spectrometer. Dissociation curves were drawn based on the intensities of precursor and product ions.RESULTSThe collision‐induced dissociation (CID) spectra of the M+ ion of each isomeric pair showed distinct product ions (3 pairs). Normal esters (1 and 3) showed abundant product ions with a neighboring group participation (NGP) reaction and reverse esters (lipid 2 and 4) showed McLafferty rearrangement product ions. The spectra of a normal amide (5) and a reverse amide (6) are similar to that found in the corresponding ester, except for the absence of the McLafferty rearrangement in 6. Dissociation curves revealed that normal esters/amide decompose at lower energy than those of corresponding reverse esters/amide.CONCLUSIONSThe lipids which easily decompose (flexible) show dramatically enhanced gene delivery capabilities and the lipids which decompose at higher collision energy (CE) values (rigid) are transfection incompetent. Copyright © 2014 John Wiley & Sons, Ltd.
Who Needs 3D When the Universe Is Flat?
Authors: ERIKSSON URBAN , LINDER CEDRIC , AIREY JOHN , REDFORS ANDREAS 
Published: April 2014

ABSTRACTAn overlooked feature in astronomy education is the need for students to learn to extrapolate three‐dimensionality and the challenges that this may involve. Discerning critical features in the night sky that are embedded in dimensionality is a long‐term learning process. Several articles have addressed the usefulness of three‐dimensional (3D) simulations in astronomy education, but they have neither addressed what students discern nor the nature of that discernment. A Web‐based questionnaire was designed using links to video clips drawn from a simulation video of travel through our galaxy and beyond. The questionnaire was completed by 137 participants from nine countries across a broad span of astronomy education. The descriptions provided by the participants were analyzed using hermeneutics in combination with a constant comparative approach to formulate six categories of discernment in relation to multidimensionality. These results are used to make the case that the ability to extrapolate three‐dimensionality calls for the creation of meaningful motion parallax experiences.
Sonographic diagnosis of lateral asynclitism: a new subtype of fetal head malposition as a main determinant of early labor arrest
Authors: Ghi T. , Bellussi F. , Pilu G. 
Published: April 2014

ABSTRACTWe report on the sonographic appearance of a new type of fetal head malposition in labor that has not been previously described systematically. In some circumstances, the fetal lie is characterized by a lateral orientation of the head with respect to the trunk and, on suprapubic ultrasound, a transverse section of the fetal chest together with the facial profile can be seen on the same image. These sonographic findings were documented in five cases of first‐stage labor arrest. This report illustrates how, in these circumstances, ultrasound might be helpful in clarifying the precise cause of obstructed labor. [[ArtCopyrightmsg]]
Thermopressurized diluted phosphoric acid pretreatment of ligno(hemi)cellulose to make free sugars and nutraceutical oligosaccharides
Authors: Tiboni Marcela , Grzybowski Adelia , Baldo Gizele Rejane , Dias Edson Flausino , Tanner Robert D , Kornfield Julia Ann , Fontana José Domingos 
Published: April 2014

Abstract
Ligno(hemi)cellulosics (L(h)Cs) as sugarcane bagasse and loblolly pine sawdust are currently being used to produce biofuels such as bioethanol and biobutanol through fermentation of free sugars that are often obtained enzymatically. However, this bioconversion requires a pretreatment to solubilize the hemicellulose fractions, thus facilitating the action of the cellulolytic enzymes. Instead of the main free monosaccharides used in these current models, the modulation of thermopressurized orthophosphoric acid as a pretreatment, in the ranges of 3–12 atm and pH 1.5–2.5, can produce nondigestible oligosaccharides (NDOS) such as xylo-oligosaccharides (XOS) because heteroxylan is present in both types of hardwood and softwood hemicelluloses. A comparative thin-layer chromatographic analysis of the hydrolytic products showed the best conditions for NDOS production to be 7 atm/water, pH 2.25 and 2.50, and 8.5 atm/water for both sources. Particular hydrolysates from 7 atm (171 °C) at pHs 2.25 and 2.50 both for cane bagasse and pine sawdust, with respective oligosaccharide contents of 57 and 59 %, once mixed in a proportion of 1:1 for each plant source, were used in vitro as carbon sources for Bifidobacterium or Lactobacillus. Once both bacteria attained the stationary phase of growth, an unforeseen feature emerged: the preference of B. animalis for bagasse hydrolysates and, conversely, the preference of L. casei for pine hydrolysates. Considering the fact that nutraceutical oligosaccharides from both hemicelluloses correspond to higher value-added byproducts, the technology using a much diluted thermopressurized orthophosphoric acid pretreatment becomes an attractive choice for L(h)Cs.
Twisted Witt Groups of Flag Varieties
Authors: Zibrowius Marcus 
Published: April 2014

AbstractCalmès and Fasel have shown that the twisted Witt groups of split flag varieties vanish in a large number of cases. For flag varieties over algebraically closed fields, we sharpen their result to an if-and-only-if statement. In particular, we show that the twisted Witt groups vanish in many previously unknown cases. In the non-zero cases, we find that the twisted total Witt group forms a free module of rank one over the untwisted total Witt group, up to a difference in grading.Our proof relies on an identification of the Witt groups of flag varieties with the Tate cohomology groups of their K-groups, whereby the verification of all assertions is eventually reduced to the computation of the (twisted) Tate cohomology of the representation ring of a parabolic subgroup.
Dissolution-driven porous-medium convection in the presence of chemical reaction
Authors: Ward T. J. , Cliffe K. A. , Jensen O. E. , Power H. 
Published: April 2014

AbstractMotivated by processes occurring during ${\mathrm{CO}}_2$ sequestration in an underground saline aquifer, we examine two-dimensional convection in a finite-depth porous medium induced by a solute introduced at the upper boundary. Once dissolved, the solute concentration is assumed to decay via a first-order chemical reaction, restricting the depth over which solute can penetrate the domain. Using spectral and asymptotic methods, we explore the resulting convective mixing using linear stability analysis, computation of nonlinear steady solution branches and time-dependent simulations, as a function of Rayleigh number, Damköhler number and domain size. Long-wave eigenmodes show how deep recirculation can be driven by a shallow solute field while explicit approximations are derived for the growth of short-wave eigenmodes. Steady solution branches undergo numerous secondary bifurcations, forming an intricate network of mixed states. Although many of these states are unstable, some play an important role in organising the phase space of time-dependent states, providing approximate bounds for time-averaged mixing rates.
Analysis of complex singularities in high-Reynolds-number Navier–Stokes solutions
Authors: Gargano F. , Sammartino M. , Sciacca V. , Cassel K. W. 
Published: April 2014

AbstractNumerical solutions of the laminar Prandtl boundary-layer and Navier–Stokes equations are considered for the case of the two-dimensional uniform flow past an impulsively-started circular cylinder. The various viscous–inviscid interactions that occur during the unsteady separation process are investigated by applying complex singularity analysis to the wall shear and streamwise velocity component of the two solutions. This is carried out using two different methodologies, namely a singularity-tracking method and the Padé approximation. It is shown how the van Dommelen and Shen singularity that occurs in solutions of the Prandtl boundary-layer equations evolves in the complex plane before leading to a separation singularity in finite time. Navier–Stokes solutions, computed at different Reynolds numbers in the range$10^3 \leq Re \leq 10^5$, are characterized by the presence of various complex singularities that can be related to different physical interactions acting over multiple spatial scales. The first interaction developing in the separation process is large-scale interaction that is visible for all the Reynolds numbers considered, and it signals the first relevant differences between the Prandtl and Navier–Stokes solutions. For$Re\geq O(10^4)$, a small-scale interaction follows the large-scale interaction. The onset of these interactions is related to the characteristic changes of the streamwise pressure gradient on the circular cylinder. Even if these interactions physically differ from that prescribed by the Prandtl solution, and they set a possible limit on the comparison of Prandtl solutions with Navier–Stokes solutions, it is shown how the asymptotic validity of boundary-layer theory is strongly supported by the results that have been obtained through the complex singularity analysis.
Transport equation for the mean turbulent energy dissipation rate in low- grid turbulence
Authors: Djenidi L. , Antonia R. A. 
Published: April 2014

AbstractA direct numerical simulation (DNS) based on the lattice Boltzmann method (LBM) is carried out in low-Reynolds-number grid turbulence to analyse the mean turbulent kinetic energy dissipation rate, $\overline{\epsilon }$, and its transport equation during decay. All the components of $\overline{\epsilon }$ and its transport equation terms are computed, providing for the first time the opportunity to assess the contribution of each term to the decay. The results indicate that although small departures from isotropy are observed in the components of $\overline{\epsilon }$ and its destruction term, there is sufficient compensation among the components for these two quantities to satisfy isotropy to a close approximation. A short distance downstream of the grid, the transport equation of $\overline{\epsilon }$ simplifies to its high-Reynolds-number homogeneous and isotropic form. The decay rate of $\overline{\epsilon }$ is governed by the imbalance between the production due to vortex stretching and the destruction caused by the action of viscosity, the latter becoming larger than the former as the distance from the grid increases. This imbalance, which is not constant during the decay as argued by Batchelor & Townsend (Proc. R. Soc. Lond. A, vol. 190, 1947, pp. 534–550), varies according to a power law of $x$, the distance downstream of the grid. The non-constancy implies a lack of dynamical similarity in the mechanisms controlling the transport of $\overline{\epsilon }$. This is consistent with the fact that the power-law-decay ($\overline{q^2} \sim x^n$) exponent $n$ is not equal to $-$1. It is actually close to $-$1.6, a value in keeping with the relatively low Reynolds number of the simulation. These results highlight the importance of the imbalance in establishing the value of $n$. The $\overline{\epsilon }$-transport equation is also analysed in relation to the power-law decay. The results show that the power-law exponent $n$ is controlled by the imbalance between production and destruction. Further, a relatively straightforward analysis provides information on the behaviour of $n$ during the entire decay process and an interesting theoretical result, which is yet to be confirmed, when $R_{\lambda } \rightarrow 0 $, namely, the destruction coefficient $G$ is constant and its value must lie between $15/7$ and $30/7$. These two limits encompass the predictions for the final period of decay by Batchelor & Townsend (1947) and Saffman (J. Fluid Mech., vol. 27, 1967, pp. 581–593).
Scattering of internal tides by irregular bathymetry of large extent
Authors: Li Yile , Mei Chiang C. 
Published: April 2014

AbstractWe present an analytical theory of scattering of tide-generated internal gravity waves in a continuously stratified ocean with a randomly rough seabed. Based on a linearized approximation, the idealized case of constant mean sea depth and Brunt–Väisälä frequency is considered. The depth fluctuation is assumed to be a stationary random function of space, characterized by small amplitude and a correlation length comparable to the typical wavelength. For both one- and two-dimensional topographies the effects of scattering on the wave phase over long distances are derived explicitly by the method of multiple scales. For one-dimensional topography, numerical results are compared with Bühler & Holmes-Cerfon (J. Fluid Mech., vol. 678, 2011, pp. 271–293), computed by the method of characteristics. For two-dimensional topography, new results are presented for both statistically isotropic and anisotropic cases.
Boundary conditions and vortex wandering
Authors: Jammy S. P. , Hills Nick , Birch David M. 
Published: April 2014

AbstractA direct numerical simulation of a Batchelor vortex has been carried out in the presence of freely decaying turbulence, using both periodic and symmetric boundary conditions; the latter most closely approximates typical experimental conditions, while the former is often used in computational simulations for numerical convenience. The higher-order velocity statistics were shown to be strongly dependent upon the boundary conditions, but the dependence could be mostly eliminated by correcting for the random, Gaussian modulation of the vortex trajectory, commonly referred to as ‘wandering’, using a technique often employed in the analysis of experimental data. Once this wandering had been corrected for, the strong peaks in the Reynolds stresses normally observed at the vortex centre were replaced by smaller local extrema located within the core region but away from the centre. The distributions of the corrected Reynolds stresses suggest that the formation and organization of secondary structures within the core is the main mechanism in turbulent production during the linear growth phase of vortex development.
A regular Strouhal number for large-scale instability in the far wake of a rotor
Authors: Okulov Valery L. , Naumov Igor V. , Mikkelsen Robert F. , Kabardin Ivan K. , Sørensen Jens N. 
Published: April 2014

AbstractThe flow behind a model of a wind turbine rotor is investigated experimentally in a water flume using particle image velocimetry (PIV) and laser Doppler anemometry (LDA). The study performed involves a three-bladed wind turbine rotor designed using the optimization technique of Glauert (Aerodynamic Theory, vol. IV, 1935, pp. 169–360). The wake properties are studied for different tip speed ratios and free stream speeds. The data for the various rotor regimes show the existence of a regular Strouhal number associated with the development of an instability in the far wake of the rotor. From visualizations and a reconstruction of the flow field using LDA and PIV measurements it is found that the wake dynamics is associated with a precession (rotation) of the helical vortex core.
Pulse dynamics in a power-law falling film
Authors: Pradas M. , Tseluiko D. , Ruyer-Quil C. , Kalliadasis S. 
Published: April 2014

AbstractWe examine the stability, dynamics and interactions of solitary waves in a two-dimensional vertically falling thin liquid film that exhibits shear-thinning effects. We use a low-dimensional two-field model that describes the evolution of both the local flow rate and the film thickness and is consistent up to second-order terms in the long-wave expansion. The shear-thinning behaviour is modelled via a power-law formulation with a Newtonian plateau in the limit of small strain rates. Our results show the emergence of a hysteresis behaviour as the control parameter (the Reynolds number) is increased which is directly related to the shear-thinning character of the liquid and can be quantified with both linear analysis arguments and a physical interpretation. We also study pulse interactions, observing that two pulses may attract or repel each other either monotonically or in an oscillatory manner. In large domains we find that for a given Reynolds number the final state depends on the initial condition, a consequence of the presence of multiple solutions.
THE TURING DEGREES BELOW GENERICS AND RANDOMS
Authors: SHORE RICHARD A. 
Published: April 2014

AbstractIf X0and X1are both generic, the theories of the degrees below X0and X1are the same. The same is true if both are random. We show that then-genericity orn-randomness of X do not suffice to guarantee that the degrees below X have these common theories. We also show that these two theories (for generics and randoms) are different. These results answer questions of Jockusch as well as Barmpalias, Day and Lewis.
INTERPRETATIONS BETWEENω-LOGIC AND SECOND-ORDER ARITHMETIC
Authors: KAYE RICHARD 
Published: April 2014

AbstractThis paper addresses the structures (M, ω) and (ω, SSy(M)), whereMis a nonstandard model of PA andωis the standard cut. It is known that (ω, SSy(M)) is interpretable in (M, ω). Our main technical result is that there is an reverse interpretation of (M, ω) in (ω, SSy(M)) which is ‘local’ in the sense of Visser [11]. We also relate the model theory of (M, ω) to the study of transplendent models of PA [2].This yields a number of model theoretic results concerning theω-models (M, ω) and their standard systems SSy(M, ω), including the following.•$\left( {M,\omega } \right) \prec \left( {K,\omega } \right)$if and only if$M \prec K$and$\left( {\omega ,{\rm{SSy}}\left( M \right)} \right) \prec \left( {\omega ,{\rm{SSy}}\left( K \right)} \right)$.•$\left( {\omega ,{\rm{SSy}}\left( M \right)} \right) \prec \left( {\omega ,{\cal P}\left( \omega \right)} \right)$if and only if$\left( {M,\omega } \right) \prec \left( {{M^{\rm{*}}},\omega } \right)$for someω-saturatedM*.•$M{ \prec _{\rm{e}}}K$implies SSy(M, ω) = SSy(K, ω), but cofinal extensions do not necessarily preserve standard system in this sense.• SSy(M, ω)=SSy(M) if and only if (ω, SSy(M)) satisfies the full comprehension scheme.• If SSy(M, ω) is uniformly defined by a single formula (analogous to aβfunction), then (ω, SSy(M, ω)) satisfies the full comprehension scheme; and there are modelsMfor which SSy(M, ω) is not uniformly defined in this sense.
FIELDS WITH SEVERAL COMMUTING DERIVATIONS
Authors: PIERCE DAVID 
Published: April 2014

AbstractFor every natural numberm, the existentially closed models of the theory of fields withmcommuting derivations can be given a first-order geometric characterization in several ways. In particular, the theory of these differential fields has a model-companion. The axioms are that certain differential varieties determined by certain ordinary varieties are nonempty. There is no restriction on the characteristic of the underlying field.
DECIDABLE MODELS OF ω-STABLE
THEORIES
Authors: ANDREWS URI 
Published: April 2014

Abstract
We characterize the ω-stable theories all of whose
countable models admit decidable presentations. In particular, we show that for
a countable ω-stable T, every
countable model of T admits a decidable presentation if and
only if all n-types in T are recursive and
T has only countably many countable models. We further
characterize the decidable models of ω-stable
theories with countably many countable models as those which realize only
recursive types.
AN INDEPENDENCE THEOREM FOR NTP2 THEORIES
Authors: YAACOV ITAÏ BEN , CHERNIKOV ARTEM 
Published: April 2014

AbstractWe establish several results regarding dividing and forking in NTP2theories. We show that dividing is the same as array-dividing. Combining it with existence of strictly invariant sequences we deduce that forking satisfies the chain condition over extension bases (namely, the forking ideal is S1, in Hrushovski’s terminology). Using it we prove an independence theorem over extension bases (which, in the case of simple theories, specializes to the ordinary independence theorem). As an application we show that Lascar strong type and compact strong type coincide over extension bases in an NTP2theory.We also define the dividing order of a theory—a generalization of Poizat’s fundamental order from stable theories—and give some equivalent characterizations under the assumption of NTP2. The last section is devoted to a refinement of the class of strong theories and its place in the classification hierarchy.