A new, modified version of the cable-suspended Ice and Bedrock Electromechanical Drill (IBED) was designed for drilling in firn, ice, debris-rich ice and rock. The upper part of the drill is almost the same for all drill variants and comprises four sections: cable termination, a slip-ring section, an antitorque system and an electronic pressure chamber. The lower part of the IBED comprises an auger core barrel, reamers, a core barrel for ice/debris-ice drilling and a conventional geological single-tube core barrel or custom-made double-tube core barrel. First, the short and full-scale field versions of the IBED were tested at an outdoor testing stand and a testing facility with a 12.5 m-deep ice well. Then, in the 2018–2019 summer season, the IBED was tested in the field at a site ~12 km south of Zhongshan Station, East Antarctica, and a ~6 cm bedrock core was recovered from a 198 m-deep borehole. A total of 18 d was required to penetrate the ice sheet. The retrieved core samples of blue ice, basal ice and bedrock provided valuable information regarding the Earth's paleo-environment.

A new type of drill bit designed with an annular slit was developed to enhance the reverse circulation effect of the down-the-hole hammer drilling technology. A computational fluid dynamics code, Fluent, was used to simulate the flow phenomena inside the drill bit. The simulation results show that the air flowing through the annular slit moves upward along the wall of the central passage of the annular drill bit and that there is no interference phenomenon similar to the normal drill bit, which is beneficial for the formation of reverse circulation. Meanwhile, the new drill bit with the annular slit was produced and tested in the laboratory. The results show that for the annular drill bit with the flushing nozzles closed, the mass flow rate of the sucked air is approximately 63.78 g/s, which is 1.76 times that of the normal drill bit, while it is about 2.46 times if the flushing nozzles are opened. In addition, many factors can affect the reverse circulation effect of the annular drill bit, including the slit width, the distance between the annular slit and the working surface of the drill bit, and the flow direction of the gas ejected from the annular slit.

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INTRODUCTION:The therapeutic effect of probiotics for irritable bowel syndrome (IBS) was controversial. This study aims to evaluate the short-term efficacy of Bifidobacterium quadruple viable tablet in patients with diarrhea-predominant IBS and explore factors associated with response to probiotics.METHODS:A randomized, double-blind, placebo-controlled, multicenter trial was performed in 15 hospitals. A total of 290 patients who fulfilled the eligibility criteria were assigned to the probiotics or placebo group randomly with a ratio of 1:1 for a 4-week treatment and a 2-week follow-up. The primary outcome was the response rate. It was regarded as the proportion of patients with composite responses of improvement in both abdominal pain and diarrhea simultaneously.RESULTS:After 4-week continuous administration, the response rates of the probiotics and the placebo were 67.59% and 36.55%, respectively (P < 0.001). In the probiotics, those with higher abdominal pain scores (2.674 [1.139–6.279]) were more likely to respond, but responders in placebo had lower Hamilton Depression Scale score (0.162 [0.060–0.439]), lower Hamilton Anxiety Scale score (0.335 [0.148–0.755]), and higher degree of bloating (2.718 [1.217–6.074]). Although the diversity of the microbiota was not significantly changed by probiotics, the abundance of bacteria producing short-chain fatty acids (SCFAs), including Butyricimonas (P = 0.048), Pseudobutyrivibrio (P = 0.005), Barnesiella (P = 0.020), and Sutterella (P = 0.020), and the concentration of SCFAs including butyric acid (P = 0.010), valeric acid (P = 0.019), and caproic acid (P = 0.046) in feces increased.DISCUSSION:A Bifidobacterium quadruple viable tablet had a significant short-term efficacy for the treatment of diarrhea-predominant IBS and was more effective in patients with higher abdominal pain scores. This kind of probiotics could improve the abundance of several bacteria producing SCFAs and the concentration of fecal SCFAs compared with placebos.

Debris-rich ice is often encountered when drilling into basal ice and rock glaciers. The standard steel bits used for ice core drilling are not suitable because the cutters are very easily broken by rock particles because their hardness and abrasiveness are higher than that of the ice. The tool steel and tungsten carbide inserts are easily damaged in intermixed ice-rock formations. To obtain high-quality core samples in debris-rich ice, it is necessary to find drill bits that can drill ice-rock mixtures with minimal load and acceptable penetration rate and torque. A special testing stand has been designed and constructed to study both standard and custom-made carbide and polycrystalline diamond compact (PDC) drill bits. The results show that both the carbide and the PDC drill bits can drill with high penetration rates in debris-rich ice containing very hard and abrasive granite particles at low drill loads of 500-1200 N. When the rock volume content is 30%, the penetration rates are 4.68 m/h, 5.9 m/h and 11.12 m/h for the standard six-tooth carbide drill bit, a PDC bit with a round compact and a PDC bit with a semi-round compact, respectively, under a drill load of 500 N with a rotation speed of 100 rpm. Within the range of drill loads of 500 to 1200 N and rotation speeds of 50 to 200 rpm, the maximum torque is no more than 45 Nm, and the power consumption is less than 0.8 kW. In addition, the temperature changes of the bit cutters caused by their cutting action were also measured. Results of the preliminary tests show that temperature variations increase from 3.67 to 5.96 ˚C when the drill load increases from 450 to 1200 N and from 4.17 to 6.21 ˚C when the rotation speed increases from 50 to 200 rpm.

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A swirling drill bit designed with an integrated vane swirler was developed to improve reverse circulation in down-the-hole hammer drilling. Its entrainment effect and influential factors were investigated by CFD simulation and experimental tests. The numerical results exhibit reasonable agreement with the experimental data, with a maximum error of 13.68%. In addition, the structural parameters of the swirler were shown to have an important effect on the reverse circulation performance of the drill bit, including the helical angle and number of spiral blades, swirler outlet area, and the flushing nozzles. The optimal parameters for the swirling drill bit without flushing nozzles include a helical angle of 60°, four spiral blades, and the area ratio of 2, while it is about 30°, 3, and 3 for the drill bit with flushing nozzles. Moreover, the entrainment ratio of the drill bit without flushing nozzles can be improved by nearly two times compared with one with flushing nozzles under the same conditions.