Implications of Color Gauge Symmetry For Nucleon Spin Structure

We study the chromodynamical gauge symmetry in relation to the internal spin structure of the nucleon. We show that 1) even in the helicity eigenstates the gauge-dependent spin and orbital angular momentum operators do not have gauge-independent matrix element; 2) the evolution equations for the gluon spin take very different forms in the Feynman and axial gauges, but yield the same leading behavior in the asymptotic limit; 3) the complete evolution of the gauge-dependent orbital angular momenta appears intractable in the light-cone gauge. We define a new gluon orbital angular momentum distribution $L_g(x)$ which {\it is} an experimental observable and has a simple scale evolution. However, its physical interpretation makes sense only in the light-cone gauge just like the gluon helicity distribution $\Delta g(x)$y.Comment: Minor corrections are made in the tex

New Spinor Field Realizations of the Non-Critical W3W_{3} String

We investigate the new spinor field realizations of the $W_{3}$ algebra, making use of the fact that the $W_{3}$ algebra can be linearized by the addition of a spin-1 current. We then use these new realizations to build the nilpotent Becchi-Rouet-Stora--Tyutin (BRST) charges of the spinor non-critical $W_{3}$ string.Comment: 8 pages, no figures, revtex4 style, accepted by Chin. Phys. Let

Functional interplay between NTP leaving group and base pair recognition during RNA polymerase II nucleotide incorporation revealed by methylene substitution.

RNA polymerase II (pol II) utilizes a complex interaction network to select and incorporate correct nucleoside triphosphate (NTP) substrates with high efficiency and fidelity. Our previous 'synthetic nucleic acid substitution' strategy has been successfully applied in dissecting the function of nucleic acid moieties in pol II transcription. However, how the triphosphate moiety of substrate influences the rate of P-O bond cleavage and formation during nucleotide incorporation is still unclear. Here, by employing β,γ-bridging atom-'substituted' NTPs, we elucidate how the methylene substitution in the pyrophosphate leaving group affects cognate and non-cognate nucleotide incorporation. Intriguingly, the effect of the β,γ-methylene substitution on the non-cognate UTP/dT scaffold (∼3-fold decrease in kpol) is significantly different from that of the cognate ATP/dT scaffold (∼130-fold decrease in kpol). Removal of the wobble hydrogen bonds in U:dT recovers a strong response to methylene substitution of UTP. Our kinetic and modeling studies are consistent with a unique altered transition state for bond formation and cleavage for UTP/dT incorporation compared with ATP/dT incorporation. Collectively, our data reveals the functional interplay between NTP triphosphate moiety and base pair hydrogen bonding recognition during nucleotide incorporation

Unshifted Metastable He I* Mini-Broad Absorption Line System in the Narrow Line Type 1 Quasar SDSS J080248.18++551328.9

We report the identification of an unusual absorption line system in the quasar SDSS J080248.18$+$551328.9 and present a detailed study of the system, incorporating follow-up optical and NIR spectroscopy. A few tens of absorption lines are detected, including He I*, Fe II* and Ni II* that arise from metastable or excited levels, as well as resonant lines in Mg I, Mg II, Fe II, Mn II, and Ca II. All of the isolated absorption lines show the same profile of width $\Delta v\sim 1,500$km s$^{-1}$ centered at a common redshift as that of the quasar emission lines, such as [O II], [S II], and hydrogen Paschen and Balmer series. With narrow Balmer lines, strong optical Fe II multiplets, and weak [O III] doublets, its emission line spectrum is typical for that of a narrow-line Seyfert 1 galaxy (NLS1). We have derived reliable measurements of the gas-phase column densities of the absorbing ions/levels. Photoionization modeling indicates that the absorber has a density of $n_{\rm H} \sim (1.0-2.5)\times 10^5~ {\rm cm}^{-3}$ and a column density of $N_{\rm H} \sim (1.0-3.2)\times 10^{21} \sim {\rm cm}^{-2}$, and is located at $R\sim100-250$ pc from the central super-massive black hole. The location of the absorber, the symmetric profile of the absorption lines, and the coincidence of the absorption and emission line centroid jointly suggest that the absorption gas is originated from the host galaxy and is plausibly accelerated by stellar processes, such as stellar winds \zhy{and/or} supernova explosions. The implications for the detection of such a peculiar absorption line system in an NLS1 are discussed in the context of co-evolution between super-massive black hole growth and host galaxy build-up.Comment: 28 pages, 16 figures; accepted for publication in Astrophysical Journa

Study on forging process of valve based on response surface method

This article takes the 21 - 4N engine valve as the research object and studies the effects of die forging temperature (1 000 - 1 180 °C), die forging speed (0,15 - 200 mm / s) and friction coefficient (0,1 - 0,5) on die forging results. First, a finite element model (FEM) of the valve blank and die is established using Creo; next, the valve forging process is simulated using Deform - 3D; then, the response surface analysis method is used to analyze and discuss the results of die forging, and to optimize the process parameters with valve product damage as the optimization goal, and determine the best process parameters for 21 - 4N engine valve forging; finally, the obtained parameters are verified through experiments, and the experimental results and prediction results have a good consistency

New insights for enhancing the performance of constructed wetlands at low temperatures.

Constructed wetlands (CWs) have been widely utilized for various types of wastewater treatment due to their merits, including high cost-effectiveness and easy operation. However, a few intrinsic drawbacks have always restricted their application and long-term stability, especially their weak performance at temperatures under 10 °C (low temperatures) due to the deterioration of microbial assimilation and plant uptake processes. The existing modifications to improve CWs performance from the direct optimization of internal components to the indirect adjunction of external resources promoted the wastewater treatment efficiency to a certain degree, but the sustainability and sufficiency of pollutants removal remains a challenge. With the goal of optimizing CW components, the integrity of the CW ecosystem and the removal of emerging pollutants, future directions for research should include radiation plant breeding, improvements to CW ecosystems, and the combination or integration of certain treatment processes with CWs to enhance wastewater treatment effects at low temperatures

Experimental study on flexural behaviour of prefabricated concrete beams with double-grouted sleeves

A novel precast concrete beam connected using double-grouted sleeves was developed to reduce pouring concrete on-site and expedite construction. This paper presents a systematic experimental study on the flexural behaviour of precast beams subjected to three-point and four-point bending. In total, 11 specimens with different types of grouted sleeves, diameters of the lower transition bar, filler lengths, numbers of filler, types of filler, types of connection and lengths of the grouted sleeve, and two cast-in-situ specimens were tested. The results indicated that the steel sleeves in the beams performed satisfactorily, and threads aided in increasing their initial stiffness. The first cracking load of all the prefabricated beams was lower than that of the reference beams owing to the interface effect. With an increase in the diameter of the lower transition bar, the yield and ultimate bearing capacities of the precast specimen under three-point bending increased by 9.0% and 21.0%, respectively. The beams with double-grouted sleeves exhibited better ductility with maximum crack widths that were 41.2% and 28.6% larger than that of the reference beam under three-point and four-point bending, respectively. The stress concentration in the filler region occurred owing to discontinuous stiffness but decreased with an increase in the diameter of the lower transition bar. The beam with double steel sleeves achieved a slightly lower normal service load limit than the cast-in-place beam. As the filler length increased by 20 mm, the maximum crack width of the beams with double-grouted sleeves increased by 55.6%. The method for the cast-in-place beam was adequate for calculating the load-bearing capacity of the prefabricated beam with double-grouted sleeves or a single-grouted sleeve

Low Frequency Coherence Break in The Soft X-ray State of GRS 1915+105

We present results from the analysis of X-ray power density spectra and coherence when GRS 1915+105 is in soft states. We use three data sets that belong to $\mu$, $\phi$ and $\delta$ classes in Belloni et al (2000). We find that the power density spectra appear to be complex, with several features between 0.01 and 10 Hz. The coherence deviates from unity above a characteristic frequency. We discuss our results in different models. The corona size in the sphere-disk model implied by this break frequency is on the order of 10$^4$ GM/c$^2$, which is unphysical. Our results are more consistent with the prediction of the model of a planar corona sustained by magnetic flares, in which the characteristic frequency is associated with the longest time-scale of an individual flare, which is about eight seconds.Comment: latex, 10 pages with 3 figure