Jet fragmentation functions in proton-proton collisions using soft-collinear effective theory

The jet fragmentation function describes the longitudinal momentum distribution of hadrons inside a reconstructed jet. We study the jet fragmentation function in proton-proton collisions in the framework of soft-collinear effective theory (SCET). We find that, up to power corrections, the jet fragmentation function can be expressed as the ratio of the fragmenting jet function and the unmeasured jet function. Using renormalization group techniques, we are able to resum large logarithms of jet radii R in the perturbative expansion of the cross section. We use our theoretical formalism to describe the jet fragmentation functions for light hadron and heavy meson production measured at the Large Hadron Collider (LHC). Our calculations agree very well with the experimental data for the light hadron production. On the other hand, although our calculations for the heavy meson production inside jets are consistent with the PYTHIA simulation, they fail to describe the LHC data. We find that the jet fragmentation function for heavy meson production is very sensitive to the gluon-to-heavy-meson fragmentation function.Comment: 26 pages, 7 figures, published version at JHE

Formation damage mechanism of a sandstone reservoir based on micro-computed tomography

Formation damage caused by well drilling, completion, oil testing, oil recovery, and stimulation seriously affects oil and gas production, the evaluation of which plays an important role in the process of oilfield development. Thus, it is necessary to study formation damage mechanism from micro scale. In this study, two sets of displacement experiments were conducted using two sandstone samples and two chemical reagents. Each set was divided into three processes: first formation water injection, reverse chemical reagents injection and second formation water injection. According to the results of displacement experiments, the permeability changes of two sandstone samples were analyzed and the formation damage rates of different experimental processes were calculated respectively. In addition, we analyzed the formation damage of the two samples from the macroscopic aspect according to the changes of inlet pressure curves. We compared the pore structure changes of sandstone samples at different experiment processes by computed tomography (CT) images, and found the particle migration phenomenon. Based on the core sensitive regions observed by CT images, the pore network models of the sensitive regions were extracted to quantitatively characterize the change of pore structure parameters (pore radius, throat radius, coordination number and tortuosity). Finally, we designed a two-dimensional microscopic seepage channel model according to the real core structure. The flow rule of solid particles in fluid was simulated by finite element method, and the reason of reservoir clogging was analyzed. Through this study, we found that the injection of chemical reagents increased the inlet pressure and led to the decrease of core permeabilities. There was a negative correlation between the export rate of particle migration and matrix deformation degree.Cited as: Wang, Z., Li, H., Lan, X., Wang, K., Yang, Y., Lisitsa, V. Formation damage mechanism of a sandstone reservoir based on micro-computed tomography. Advances in Geo-Energy Research, 2021, 5(1): 25-38, doi: 10.46690/ager.2021.01.0

The evaluation of biological productivity by triple isotope composition of oxygen trapped in ice-core bubbles and dissolved in ocean: a review

The 17O anomaly of oxygen (Δ17O, calculated from δ17O and δ18O) trapped in ice-core bubbles and dissolved in ocean has been respectively used to evaluate the past biosphere productivity at a global scale and gross oxygen production (GOP) in the mixed layer (ML) of ocean. Compared to traditional methods in GOP estimation, triple oxygen isotope (TOI) method provides estimates that ignore incubation bottle effects and calculates GOP on larger spatial and temporal scales. Calculated from TOI of O2 trapped in ice-core bubbles, the averaged global biological productivities in past glacial periods were about 0.83–0.94 of the present, and the longest time record reached 400 ka BP (thousand years before the present). TOI-derived GOP estimation has also been widely applied in open oceans and coastal oceans, with emphasis on the ML. Although the TOI method has been widely used in aquatic ecosystems, TOI-based GOP is assumed to be constant at a steady state, and the influence of physical transports below the ML is neglected. The TOI method applied to evaluate past total biospheric productivity is limited by rare samples as well as uncertainties related to O2 consumption mechanisms and terrestrial biosphere’s hydrological processes. Future studies should take into account the physical transports below the ML and apply the TOI method in deep ocean. In addition, study on the complex land biosphere mechanisms by triple isotope composition of O2 trapped in ice-core bubbles needs to be strengthened

High-detectivity ultraviolet photodetectors based on laterally mesoporous GaN

Photodetectors for the ultraviolet (UV) range of the electromagnetic spectrum are in great demand for several technologies, but require the development of novel device structures and materials. Here we report on the high detectivity of UV photodetectors based on well-ordered laterally mesoporous GaN. The specific detectivity of our devices under UV-illumination reaches values of up to 5.3×1014 Jones. We attribute this high specific detectivity to the properties of the mesoporous GaN/metal contact interface: the trapping of photo-generated holes at the interface lowers the Schottky barrier height thus causing a large internal gain. The high detectivity along with the simple fabrication process make these laterally mesoporous GaN photodetectors of great potential for applications that require selective detection of weak optical signals in the UV range

Response of "Glacier-Runoff" system in a typical monsoonal temperate glacier region, Hailuogou Basin in Mt. Gongga of China, to global warming

International audienceThe method of correlation analysis and trend analysis were used in this research in order to confirm the response of "glacier-runoff" system to global warming. Hailuogou glacier had retreated by 1871.8 m over the past 76 years, Hailuogou No. 2 glacier had also retreated by 1100 m. Glaciers retreats are contrary to the climatic warming trend in China and the Northern Hemisphere. Glaciers in Hailuogou basin were in the loss with a fluctuating manner since 1950s, and accumulative value of mass balance is ?10 825.5 mm water equivalent with an annual mean value of ?240.6 mm. The inverse correlation is highly significant between mass balance variation and climatic fluctuation of China and the Northern Hemisphere after 1950s. Glacier ablation is intensive with a ratio of 7.86 m yr?1. A steady rise tendency toward glaciers runoff has been observed since 1980s, and the runoff rise is mainly responsible for melt water in Hailuogou basin. It is noticeable that climatic warming not only strengthened ablation extent and enlarged ablation area, but also prolonged ablation period. Global warming is the main cause of glacier retreat, mass loss and runoff rise in Hailuogou basin

Study of Expressway Service Area Function Expansion

With the rapid development of economy and society, in the face of an increasingly large expressway consumer group, the expansion and upgrading of the expressway service area to marketization and industrialization is the only way for the sustainable development of the service area. The service area should be adapted to local conditions when expanding functions, and be expanded in a targeted manner according to the characteristics of each service area

Studies on the Developmental Potentiality of Cultured Cell Nuclei of Fish

<p>By means of the serial nuclear transplantation technique, the authors obtained a nuclear transplant fish from subcultured cell originated from the blastula cells of the crucian carp (<i>Carassius auratus </i>Linnaeus)<i>. </i>This nuclear transplant fish survived for three years, but its sexual glands were undifferentiated. The authors have also obtained a sexually mature adult fish from short-term cultured kidney cell nucleus of an adult crucian carp.</p> <p>Results of the experiment implied that the subcultured cell nuclei of fish blastula cells and the specialized somatic cell nuclei of adult fish still retained their developmental totipotency, and thus, it indicated that there is a possibility of fish somatic cell breeding through the use of nuclear transplantation.</p