Force and deformation characteristics during the reconstruction and expansion of shallow single-tube tunnels into large-span multiarch tunnels

At present, there are an ever-increasing number of tunnel expansion projects in China. Studying the mechanical properties of the expanded tunnels is of great significance for guiding their safe construction. Through model testing and numerical simulation, the mechanical properties of a double-arch tunnel constructed through the expansion of the middle pilot heading from an existing single-tube tunnel were studied. The variation characteristics of the surface subsidence, surrounding rock stress, and stress and strain of the middle partition wall and lining during the tunnel reconstruction and expansion were investigated. The mechanism for transferring stress and strain between the left and right tunnel tubes was studied by a numerical simulation method. The results showed that the surface subsidence caused by the excavation of the left (i.e., the subsequent) tunnel tube was larger, and the maximum surface subsidence occurred at the right (i.e., the first) tunnel tube. The surrounding rock on the middle wall was the sensitive part of the tunnel excavation, the stress of the surrounding rock at the left spandrel of the right tunnel tube fluctuated and exhibited the most complex variation, and the stress of the surrounding rock at the right spandrel of the left tunnel tube exhibited the largest variation. The excavation of the left tunnel tube had a great influence on the forces of the middle partition wall and the lining structure of the right tunnel tube, the middle partition wall was subjected to eccentric compression towards the left tunnel tube, and the stress at the left spandrel under the initial support of the right tunnel tube exhibited complex variations. The excavation of the left and right tunnel tubes had a great influence on the stability of the surrounding rock, as well as on the force-induced deformation of the middle partition wall and the support structure, within the width of the single tunnel tube span behind the tunnel working face. Due to the different construction sequences, the stress and strain at the symmetric measurement points of the middle partition wall, as well as the left and right tunnel support structures, were very different

Impact of maternal reproductive factors on cancer risks of offspring : a systematic review and meta-analysis of cohort studies

BackgroundA number of studies have reported on associations between reproductive factors, such as delivery methods, number of birth and breastfeeding, and incidence of cancer in children, but systematic reviews addressing this issue to date have important limitations, and no reviews have addressed the impact of reproductive factors on cancer over the full life course of offspring.MethodsWe performed a comprehensive search in MEDLINE, and Embase up to January 2020 and Web of Science up to 2018 July, including cohort studies reporting the association between maternal reproductive factors of age at birth, birth order, number of births, delivery methods, and breastfeeding duration and cancer in children. Teams of two reviewers independently extracted data and assessed risk of bias. We conducted random effects meta-analyses to estimate summary relative estimates, calculated absolute differences between those with and without risk factors, and used the GRADE approach to evaluate the certainty of evidence.ResultsFor most exposures and most cancers, we found no suggestion of a causal relation. We found low to very low certainty evidence of the following very small possible impact: higher maternal age at birth with adult multiple myeloma and lifetime uterine cervix cancer incidence; lower maternal age at birth with childhood overall cancer mortality (RR = 1.15, 95% CI = 1.01-1.30; AR/10,000 = 1, 95% CI = 0 to 2), adult leukemia and lifetime uterine cervix cancer incidence; higher birth order with adult melanoma, cervix uteri, corpus uteri, thyroid cancer incidence, lifetime lung, corpus uteri, prostate, testis, sarcoma, thyroid cancer incidence; larger number of birth with childhood brain (RR = 1.27, 95% CI = 1.06-1.52; AR/10,000 = 1, 95% CI = 0 to 2), leukemia (RR = 2.11, 95% CI = 1.62-2.75; AR/10,000 = 9, 95% CI = 5 to 14), lymphoma (RR = 4.66, 95% CI = 1.40-15.57; AR/10,000 = 11, 95% CI = 1 to 44) incidence, adult stomach, corpus uteri cancer incidence and lung cancer mortality, lifetime stomach, lung, uterine cervix, uterine corpus, multiple myeloma, testis cancer incidence; Caesarean delivery with childhood kidney cancer incidence (RR = 1.25, 95% CI = 1.01-1.55; AR/10,000 = 0, 95% CI = 0 to 1); and breastfeeding with adult colorectal cancer incidence.ConclusionVery small impacts existed between a number of reproductive factors and cancer incidence and mortality in children and the certainty of evidence was low to very low primarily due to observational design

Improvement of n-caproic acid production with Ruminococcaceae bacterium CPB6: selection of electron acceptors and carbon sources and optimization of the culture medium

Abstract Background Global energy and resource shortages make it necessary to quest for renewable resources. n-Caproic acid (CA) production based on carboxylate platform by anaerobic fermentation is booming. Recently, a novel Ruminococcaceae bacterium CPB6 is shown to be a potential biotransformation factory for CA production from lactate-containing wastewater. However, little is known about the effects of different electron acceptors (EAs) on the fermentative products of strain CPB6, as well as the optimum medium for CA production. Results In this study, batch experiments were performed to investigate the fermentative products of strain CPB6 in a lactate medium supplemented with different EAs and sugars. Supplementation of acetate, butyrate and sucrose dramatically increased cell growth and CA production. The addition of propionate or pentanoate resulted in the production of C5 or C7 carboxylic acid, respectively. Further, a Box–Behnken experiment was conducted to optimize the culture medium for CA production. The result indicated that a medium containing 13.30 g/L sucrose, 22.35 g/L lactate and 16.48 g/L butyrate supported high-titer CA production (16.73 g/L) with a maximum productivity of 6.50 g/L/day. Conclusions This study demonstrated that strain CPB6 could produce C6–C7 carboxylic acids from lactate (as electron donor) with C2–C5 short-chain carboxylic acids (as EAs), but CA (C6 carboxylic acid) was the most major and potential product. Butyrate and sucrose were the most significant EA and carbon source respectively for CA production from lactate by strain CPB6. High titer of CA can be produced from a synthetic substrate containing sucrose, lactate and butyrate. The work provided significant implications for improving CA production in industry-scale

Daily changes in spatial accessibility to intensive care unit (ICU) beds and their relationship with the case-fatality ratio of COVID-19 in the state of Texas

This dataset and code are presented to explain a manuscript entitled "Daily changes in spatial accessibility to intensive care unit (ICU) beds and their relationship with the case-fatality ratio of COVID-19 in the state of Texas", which is under review in Health & Place. To run the code properly, data.zip should be unzipped in the same directory with the other files ('Daily changes in spatial accessibility to ICU beds during the COVID-19 pandemic.ipynb' and 'utils.py'). </p

Super-long aligned TiO 2 /carbon nanotube arrays Super-long aligned TiO 2 /carbon nanotube arrays

Abstract 5 mm long aligned titanium oxide/carbon nanotube (TiO 2 /CNT) coaxial nanowire arrays have been prepared by electrochemically coating the constituent CNTs with a uniform layer of highly crystalline anatase TiO 2 nanoparticles. While the presence of the TiO 2 coating was confirmed by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and x-ray diffraction, the resultant TiO 2 /CNT coaxial arrays were demonstrated to exhibit minimized recombination of photoinduced electron-hole pairs and fast electron transfer from the long TiO 2 /CNT arrays to external circuits. This, in conjunction with the aligned macrostructure, facilitates the fabrication of TiO 2 /CNT arrays for various device applications, ranging from photodetectors to photocatalytic systems. Thus, the millimeter long TiO 2 /CNT arrays represent a significant advance in the development of new macroscopic photoelectronic nanomaterials attractive for a variety of device applications beyond those demonstrated in this study

Enhanced support effects in single-atom copper-incorporated carbon nitride for photocatalytic suzuki cross-coupling reactions

Conditioning the nature of metal active sites for better performance by well designing and constructing the support material is always appealing in heterogeneous catalysis. Herein, Cu species was introduced into the bulk phase of carbon nitride to strengthen the interlayer connection and optimize the electronic structure. The resulting material (CN-Cu) demonstrated an enhanced support effect for Pd catalyzed Suzuki cross-coupling reactions under light illumination. Detailed characterizations showed that Cu species were atomically incorporated in intra/interlayer of CN framework through coordinating with pyridinic nitrogen, leading to improved light absorption and more efficient charge carrier transfer. More importantly, the electronic effect of CN-Cu to the surface Pd was enhanced by the electron drift from Cu to N, thereby rendered an electron-rich Pd surface. Such Pd surfaces allowed faster electron injection from Pd(0) to the LUMO of aryl halides and therefore accelerate the rate-determining step of the coupling reaction.</p